LukeSheard/Monzo-Dashboard

View on GitHub

Showing 63 of 63 total issues

Identical blocks of code found in 3 locations. Consider refactoring.
Open

  getControlId() {
    const {
      label,
      placeholder,
    } = this.props;
Severity: Major
Found in src/common/components/form/field.jsx and 2 other locations - About 1 hr to fix
src/common/components/form/date.jsx on lines 53..60
src/common/components/form/select.jsx on lines 38..45

Duplicated Code

Duplicated code can lead to software that is hard to understand and difficult to change. The Don't Repeat Yourself (DRY) principle states:

Every piece of knowledge must have a single, unambiguous, authoritative representation within a system.

When you violate DRY, bugs and maintenance problems are sure to follow. Duplicated code has a tendency to both continue to replicate and also to diverge (leaving bugs as two similar implementations differ in subtle ways).

Tuning

This issue has a mass of 61.

We set useful threshold defaults for the languages we support but you may want to adjust these settings based on your project guidelines.

The threshold configuration represents the minimum mass a code block must have to be analyzed for duplication. The lower the threshold, the more fine-grained the comparison.

If the engine is too easily reporting duplication, try raising the threshold. If you suspect that the engine isn't catching enough duplication, try lowering the threshold. The best setting tends to differ from language to language.

See codeclimate-duplication's documentation for more information about tuning the mass threshold in your .codeclimate.yml.

Refactorings

Further Reading

Identical blocks of code found in 3 locations. Consider refactoring.
Open

  getControlId() {
    const {
      label,
      placeholder,
    } = this.props;
Severity: Major
Found in src/common/components/form/date.jsx and 2 other locations - About 1 hr to fix
src/common/components/form/field.jsx on lines 42..49
src/common/components/form/select.jsx on lines 38..45

Duplicated Code

Duplicated code can lead to software that is hard to understand and difficult to change. The Don't Repeat Yourself (DRY) principle states:

Every piece of knowledge must have a single, unambiguous, authoritative representation within a system.

When you violate DRY, bugs and maintenance problems are sure to follow. Duplicated code has a tendency to both continue to replicate and also to diverge (leaving bugs as two similar implementations differ in subtle ways).

Tuning

This issue has a mass of 61.

We set useful threshold defaults for the languages we support but you may want to adjust these settings based on your project guidelines.

The threshold configuration represents the minimum mass a code block must have to be analyzed for duplication. The lower the threshold, the more fine-grained the comparison.

If the engine is too easily reporting duplication, try raising the threshold. If you suspect that the engine isn't catching enough duplication, try lowering the threshold. The best setting tends to differ from language to language.

See codeclimate-duplication's documentation for more information about tuning the mass threshold in your .codeclimate.yml.

Refactorings

Further Reading

Function render has 30 lines of code (exceeds 25 allowed). Consider refactoring.
Open

  render() {
    const {
      onCancel,
      signOut,
    } = this.props;
Severity: Minor
Found in src/common/routes/sign-out/index.jsx - About 1 hr to fix

    Function render has 27 lines of code (exceeds 25 allowed). Consider refactoring.
    Open

      render() {
        const {
          date,
          transactions,
        } = this.props;
    Severity: Minor
    Found in src/common/components/transaction-list/group/index.jsx - About 1 hr to fix

      Function default has 26 lines of code (exceeds 25 allowed). Consider refactoring.
      Open

      export default function (history = createMemoryHistory(), initialState = {}) {
        const sagaMiddleware = createSagaMiddleware();
      
        let plugins;
        if (_DEV_) {
      Severity: Minor
      Found in src/common/store/index.js - About 1 hr to fix

        Function start has 26 lines of code (exceeds 25 allowed). Consider refactoring.
        Open

        export function start() {
          const {
            CLIENT_ID,
            CLIENT_SECRET,
            STATE_TOKEN,
        Severity: Minor
        Found in src/server/index.js - About 1 hr to fix

          Similar blocks of code found in 2 locations. Consider refactoring.
          Open

              const {
                children,
                error,
                label,
                onBlur,
          Severity: Minor
          Found in src/common/components/form/select.jsx and 1 other location - About 50 mins to fix
          src/common/components/transaction-list/transaction/index.jsx on lines 33..42

          Duplicated Code

          Duplicated code can lead to software that is hard to understand and difficult to change. The Don't Repeat Yourself (DRY) principle states:

          Every piece of knowledge must have a single, unambiguous, authoritative representation within a system.

          When you violate DRY, bugs and maintenance problems are sure to follow. Duplicated code has a tendency to both continue to replicate and also to diverge (leaving bugs as two similar implementations differ in subtle ways).

          Tuning

          This issue has a mass of 52.

          We set useful threshold defaults for the languages we support but you may want to adjust these settings based on your project guidelines.

          The threshold configuration represents the minimum mass a code block must have to be analyzed for duplication. The lower the threshold, the more fine-grained the comparison.

          If the engine is too easily reporting duplication, try raising the threshold. If you suspect that the engine isn't catching enough duplication, try lowering the threshold. The best setting tends to differ from language to language.

          See codeclimate-duplication's documentation for more information about tuning the mass threshold in your .codeclimate.yml.

          Refactorings

          Further Reading

          Identical blocks of code found in 3 locations. Consider refactoring.
          Open

            getValidationState() {
              const {
                error,
                invalid,
                touched,
          Severity: Major
          Found in src/common/components/form/field.jsx and 2 other locations - About 50 mins to fix
          src/common/components/form/date.jsx on lines 62..74
          src/common/components/form/select.jsx on lines 47..59

          Duplicated Code

          Duplicated code can lead to software that is hard to understand and difficult to change. The Don't Repeat Yourself (DRY) principle states:

          Every piece of knowledge must have a single, unambiguous, authoritative representation within a system.

          When you violate DRY, bugs and maintenance problems are sure to follow. Duplicated code has a tendency to both continue to replicate and also to diverge (leaving bugs as two similar implementations differ in subtle ways).

          Tuning

          This issue has a mass of 52.

          We set useful threshold defaults for the languages we support but you may want to adjust these settings based on your project guidelines.

          The threshold configuration represents the minimum mass a code block must have to be analyzed for duplication. The lower the threshold, the more fine-grained the comparison.

          If the engine is too easily reporting duplication, try raising the threshold. If you suspect that the engine isn't catching enough duplication, try lowering the threshold. The best setting tends to differ from language to language.

          See codeclimate-duplication's documentation for more information about tuning the mass threshold in your .codeclimate.yml.

          Refactorings

          Further Reading

          Identical blocks of code found in 3 locations. Consider refactoring.
          Open

            getValidationState() {
              const {
                error,
                invalid,
                touched,
          Severity: Major
          Found in src/common/components/form/select.jsx and 2 other locations - About 50 mins to fix
          src/common/components/form/date.jsx on lines 62..74
          src/common/components/form/field.jsx on lines 51..63

          Duplicated Code

          Duplicated code can lead to software that is hard to understand and difficult to change. The Don't Repeat Yourself (DRY) principle states:

          Every piece of knowledge must have a single, unambiguous, authoritative representation within a system.

          When you violate DRY, bugs and maintenance problems are sure to follow. Duplicated code has a tendency to both continue to replicate and also to diverge (leaving bugs as two similar implementations differ in subtle ways).

          Tuning

          This issue has a mass of 52.

          We set useful threshold defaults for the languages we support but you may want to adjust these settings based on your project guidelines.

          The threshold configuration represents the minimum mass a code block must have to be analyzed for duplication. The lower the threshold, the more fine-grained the comparison.

          If the engine is too easily reporting duplication, try raising the threshold. If you suspect that the engine isn't catching enough duplication, try lowering the threshold. The best setting tends to differ from language to language.

          See codeclimate-duplication's documentation for more information about tuning the mass threshold in your .codeclimate.yml.

          Refactorings

          Further Reading

          Identical blocks of code found in 3 locations. Consider refactoring.
          Open

            getValidationState() {
              const {
                error,
                invalid,
                touched,
          Severity: Major
          Found in src/common/components/form/date.jsx and 2 other locations - About 50 mins to fix
          src/common/components/form/field.jsx on lines 51..63
          src/common/components/form/select.jsx on lines 47..59

          Duplicated Code

          Duplicated code can lead to software that is hard to understand and difficult to change. The Don't Repeat Yourself (DRY) principle states:

          Every piece of knowledge must have a single, unambiguous, authoritative representation within a system.

          When you violate DRY, bugs and maintenance problems are sure to follow. Duplicated code has a tendency to both continue to replicate and also to diverge (leaving bugs as two similar implementations differ in subtle ways).

          Tuning

          This issue has a mass of 52.

          We set useful threshold defaults for the languages we support but you may want to adjust these settings based on your project guidelines.

          The threshold configuration represents the minimum mass a code block must have to be analyzed for duplication. The lower the threshold, the more fine-grained the comparison.

          If the engine is too easily reporting duplication, try raising the threshold. If you suspect that the engine isn't catching enough duplication, try lowering the threshold. The best setting tends to differ from language to language.

          See codeclimate-duplication's documentation for more information about tuning the mass threshold in your .codeclimate.yml.

          Refactorings

          Further Reading

          Similar blocks of code found in 2 locations. Consider refactoring.
          Open

              const {
                amount,
                currency,
                date,
                description,
          Severity: Minor
          Found in src/common/components/transaction-list/transaction/index.jsx and 1 other location - About 50 mins to fix
          src/common/components/form/select.jsx on lines 62..71

          Duplicated Code

          Duplicated code can lead to software that is hard to understand and difficult to change. The Don't Repeat Yourself (DRY) principle states:

          Every piece of knowledge must have a single, unambiguous, authoritative representation within a system.

          When you violate DRY, bugs and maintenance problems are sure to follow. Duplicated code has a tendency to both continue to replicate and also to diverge (leaving bugs as two similar implementations differ in subtle ways).

          Tuning

          This issue has a mass of 52.

          We set useful threshold defaults for the languages we support but you may want to adjust these settings based on your project guidelines.

          The threshold configuration represents the minimum mass a code block must have to be analyzed for duplication. The lower the threshold, the more fine-grained the comparison.

          If the engine is too easily reporting duplication, try raising the threshold. If you suspect that the engine isn't catching enough duplication, try lowering the threshold. The best setting tends to differ from language to language.

          See codeclimate-duplication's documentation for more information about tuning the mass threshold in your .codeclimate.yml.

          Refactorings

          Further Reading

          Similar blocks of code found in 2 locations. Consider refactoring.
          Open

                    <Col xs={6} md={4}>
                      <DateField
                        label="End Date"
                        {...endDate}
                        todayButton
          Severity: Minor
          Found in src/common/components/transaction-list/filters/index.jsx and 1 other location - About 40 mins to fix
          src/common/components/transaction-list/filters/index.jsx on lines 47..54

          Duplicated Code

          Duplicated code can lead to software that is hard to understand and difficult to change. The Don't Repeat Yourself (DRY) principle states:

          Every piece of knowledge must have a single, unambiguous, authoritative representation within a system.

          When you violate DRY, bugs and maintenance problems are sure to follow. Duplicated code has a tendency to both continue to replicate and also to diverge (leaving bugs as two similar implementations differ in subtle ways).

          Tuning

          This issue has a mass of 48.

          We set useful threshold defaults for the languages we support but you may want to adjust these settings based on your project guidelines.

          The threshold configuration represents the minimum mass a code block must have to be analyzed for duplication. The lower the threshold, the more fine-grained the comparison.

          If the engine is too easily reporting duplication, try raising the threshold. If you suspect that the engine isn't catching enough duplication, try lowering the threshold. The best setting tends to differ from language to language.

          See codeclimate-duplication's documentation for more information about tuning the mass threshold in your .codeclimate.yml.

          Refactorings

          Further Reading

          Similar blocks of code found in 2 locations. Consider refactoring.
          Open

                  <Provider store={store}>
                    <IntlProvider locale="en">
                      <RouterContext {...renderProps} />
                    </IntlProvider>
                  </Provider>
          Severity: Minor
          Found in src/server/html/index.jsx and 1 other location - About 40 mins to fix
          src/client/index.jsx on lines 53..57

          Duplicated Code

          Duplicated code can lead to software that is hard to understand and difficult to change. The Don't Repeat Yourself (DRY) principle states:

          Every piece of knowledge must have a single, unambiguous, authoritative representation within a system.

          When you violate DRY, bugs and maintenance problems are sure to follow. Duplicated code has a tendency to both continue to replicate and also to diverge (leaving bugs as two similar implementations differ in subtle ways).

          Tuning

          This issue has a mass of 48.

          We set useful threshold defaults for the languages we support but you may want to adjust these settings based on your project guidelines.

          The threshold configuration represents the minimum mass a code block must have to be analyzed for duplication. The lower the threshold, the more fine-grained the comparison.

          If the engine is too easily reporting duplication, try raising the threshold. If you suspect that the engine isn't catching enough duplication, try lowering the threshold. The best setting tends to differ from language to language.

          See codeclimate-duplication's documentation for more information about tuning the mass threshold in your .codeclimate.yml.

          Refactorings

          Further Reading

          Similar blocks of code found in 2 locations. Consider refactoring.
          Open

                <Provider store={store} >
                  <IntlProvider locale="en">
                    <Router {...renderProps} />
                  </IntlProvider>
                </Provider>
          Severity: Minor
          Found in src/client/index.jsx and 1 other location - About 40 mins to fix
          src/server/html/index.jsx on lines 54..58

          Duplicated Code

          Duplicated code can lead to software that is hard to understand and difficult to change. The Don't Repeat Yourself (DRY) principle states:

          Every piece of knowledge must have a single, unambiguous, authoritative representation within a system.

          When you violate DRY, bugs and maintenance problems are sure to follow. Duplicated code has a tendency to both continue to replicate and also to diverge (leaving bugs as two similar implementations differ in subtle ways).

          Tuning

          This issue has a mass of 48.

          We set useful threshold defaults for the languages we support but you may want to adjust these settings based on your project guidelines.

          The threshold configuration represents the minimum mass a code block must have to be analyzed for duplication. The lower the threshold, the more fine-grained the comparison.

          If the engine is too easily reporting duplication, try raising the threshold. If you suspect that the engine isn't catching enough duplication, try lowering the threshold. The best setting tends to differ from language to language.

          See codeclimate-duplication's documentation for more information about tuning the mass threshold in your .codeclimate.yml.

          Refactorings

          Further Reading

          Similar blocks of code found in 2 locations. Consider refactoring.
          Open

                    <Col xs={6} md={4}>
                      <DateField
                        label="Start Date"
                        {...startDate}
                        todayButton
          Severity: Minor
          Found in src/common/components/transaction-list/filters/index.jsx and 1 other location - About 40 mins to fix
          src/common/components/transaction-list/filters/index.jsx on lines 55..62

          Duplicated Code

          Duplicated code can lead to software that is hard to understand and difficult to change. The Don't Repeat Yourself (DRY) principle states:

          Every piece of knowledge must have a single, unambiguous, authoritative representation within a system.

          When you violate DRY, bugs and maintenance problems are sure to follow. Duplicated code has a tendency to both continue to replicate and also to diverge (leaving bugs as two similar implementations differ in subtle ways).

          Tuning

          This issue has a mass of 48.

          We set useful threshold defaults for the languages we support but you may want to adjust these settings based on your project guidelines.

          The threshold configuration represents the minimum mass a code block must have to be analyzed for duplication. The lower the threshold, the more fine-grained the comparison.

          If the engine is too easily reporting duplication, try raising the threshold. If you suspect that the engine isn't catching enough duplication, try lowering the threshold. The best setting tends to differ from language to language.

          See codeclimate-duplication's documentation for more information about tuning the mass threshold in your .codeclimate.yml.

          Refactorings

          Further Reading

          Import in body of module; reorder to top.
          Open

          import {

          For more information visit Source: http://eslint.org/docs/rules/

          Missing trailing comma.
          Open

                }
          Severity: Minor
          Found in src/common/store/balance/saga.js by eslint

          require or disallow trailing commas (comma-dangle)

          Trailing commas in object literals are valid according to the ECMAScript 5 (and ECMAScript 3!) spec. However, IE8 (when not in IE8 document mode) and below will throw an error when it encounters trailing commas in JavaScript.

          var foo = {
              bar: "baz",
              qux: "quux",
          };

          Trailing commas simplify adding and removing items to objects and arrays, since only the lines you are modifying must be touched. Another argument in favor of trailing commas is that it improves the clarity of diffs when an item is added or removed from an object or array:

          Less clear:

          var foo = {
          -    bar: "baz",
          -    qux: "quux"
          +    bar: "baz"
           };

          More clear:

          var foo = {
               bar: "baz",
          -    qux: "quux",
           };

          Rule Details

          This rule enforces consistent use of trailing commas in object and array literals.

          Options

          This rule has a string option or an object option:

          {
              "comma-dangle": ["error", "never"],
              // or
              "comma-dangle": ["error", {
                  "arrays": "never",
                  "objects": "never",
                  "imports": "never",
                  "exports": "never",
                  "functions": "ignore",
              }]
          }
          • "never" (default) disallows trailing commas
          • "always" requires trailing commas
          • "always-multiline" requires trailing commas when the last element or property is in a different line than the closing ] or } and disallows trailing commas when the last element or property is on the same line as the closing ] or }
          • "only-multiline" allows (but does not require) trailing commas when the last element or property is in a different line than the closing ] or } and disallows trailing commas when the last element or property is on the same line as the closing ] or }

          Trailing commas in function declarations and function calls are valid syntax since ECMAScript 2017; however, the string option does not check these situations for backwards compatibility.

          You can also use an object option to configure this rule for each type of syntax. Each of the following options can be set to "never", "always", "always-multiline", "only-multiline", or "ignore". The default for each option is "never" unless otherwise specified.

          • arrays is for array literals and array patterns of destructuring. (e.g. let [a,] = [1,];)
          • objects is for object literals and object patterns of destructuring. (e.g. let {a,} = {a: 1};)
          • imports is for import declarations of ES Modules. (e.g. import {a,} from "foo";)
          • exports is for export declarations of ES Modules. (e.g. export {a,};)
          • functions is for function declarations and function calls. (e.g. (function(a,){ })(b,);)
            functions is set to "ignore" by default for consistency with the string option.

          never

          Examples of incorrect code for this rule with the default "never" option:

          /*eslint comma-dangle: ["error", "never"]*/
          
          var foo = {
              bar: "baz",
              qux: "quux",
          };
          
          var arr = [1,2,];
          
          foo({
            bar: "baz",
            qux: "quux",
          });

          Examples of correct code for this rule with the default "never" option:

          /*eslint comma-dangle: ["error", "never"]*/
          
          var foo = {
              bar: "baz",
              qux: "quux"
          };
          
          var arr = [1,2];
          
          foo({
            bar: "baz",
            qux: "quux"
          });

          always

          Examples of incorrect code for this rule with the "always" option:

          /*eslint comma-dangle: ["error", "always"]*/
          
          var foo = {
              bar: "baz",
              qux: "quux"
          };
          
          var arr = [1,2];
          
          foo({
            bar: "baz",
            qux: "quux"
          });

          Examples of correct code for this rule with the "always" option:

          /*eslint comma-dangle: ["error", "always"]*/
          
          var foo = {
              bar: "baz",
              qux: "quux",
          };
          
          var arr = [1,2,];
          
          foo({
            bar: "baz",
            qux: "quux",
          });

          always-multiline

          Examples of incorrect code for this rule with the "always-multiline" option:

          /*eslint comma-dangle: ["error", "always-multiline"]*/
          
          var foo = {
              bar: "baz",
              qux: "quux"
          };
          
          var foo = { bar: "baz", qux: "quux", };
          
          var arr = [1,2,];
          
          var arr = [1,
              2,];
          
          var arr = [
              1,
              2
          ];
          
          foo({
            bar: "baz",
            qux: "quux"
          });

          Examples of correct code for this rule with the "always-multiline" option:

          /*eslint comma-dangle: ["error", "always-multiline"]*/
          
          var foo = {
              bar: "baz",
              qux: "quux",
          };
          
          var foo = {bar: "baz", qux: "quux"};
          var arr = [1,2];
          
          var arr = [1,
              2];
          
          var arr = [
              1,
              2,
          ];
          
          foo({
            bar: "baz",
            qux: "quux",
          });

          only-multiline

          Examples of incorrect code for this rule with the "only-multiline" option:

          /*eslint comma-dangle: ["error", "only-multiline"]*/
          
          var foo = { bar: "baz", qux: "quux", };
          
          var arr = [1,2,];
          
          var arr = [1,
              2,];

          Examples of correct code for this rule with the "only-multiline" option:

          /*eslint comma-dangle: ["error", "only-multiline"]*/
          
          var foo = {
              bar: "baz",
              qux: "quux",
          };
          
          var foo = {
              bar: "baz",
              qux: "quux"
          };
          
          var foo = {bar: "baz", qux: "quux"};
          var arr = [1,2];
          
          var arr = [1,
              2];
          
          var arr = [
              1,
              2,
          ];
          
          var arr = [
              1,
              2
          ];
          
          foo({
            bar: "baz",
            qux: "quux",
          });
          
          foo({
            bar: "baz",
            qux: "quux"
          });

          functions

          Examples of incorrect code for this rule with the {"functions": "never"} option:

          /*eslint comma-dangle: ["error", {"functions": "never"}]*/
          
          function foo(a, b,) {
          }
          
          foo(a, b,);
          new foo(a, b,);

          Examples of correct code for this rule with the {"functions": "never"} option:

          /*eslint comma-dangle: ["error", {"functions": "never"}]*/
          
          function foo(a, b) {
          }
          
          foo(a, b);
          new foo(a, b);

          Examples of incorrect code for this rule with the {"functions": "always"} option:

          /*eslint comma-dangle: ["error", {"functions": "always"}]*/
          
          function foo(a, b) {
          }
          
          foo(a, b);
          new foo(a, b);

          Examples of correct code for this rule with the {"functions": "always"} option:

          /*eslint comma-dangle: ["error", {"functions": "always"}]*/
          
          function foo(a, b,) {
          }
          
          foo(a, b,);
          new foo(a, b,);

          When Not To Use It

          You can turn this rule off if you are not concerned with dangling commas. Source: http://eslint.org/docs/rules/

          Import in body of module; reorder to top.
          Open

          import webpackConfig from 'webpack.config.babel'; // eslint-disable-line import/no-unresolved
          Severity: Minor
          Found in src/server/app.js by eslint

          For more information visit Source: http://eslint.org/docs/rules/

          Unexpected parentheses around single function argument having a body with no curly braces
          Open

            const sagas = components.filter((component) => component && component.preload)
          Severity: Minor
          Found in src/server/render/waitForAll.js by eslint

          Require parens in arrow function arguments (arrow-parens)

          Arrow functions can omit parentheses when they have exactly one parameter. In all other cases the parameter(s) must be wrapped in parentheses. This rule enforces the consistent use of parentheses in arrow functions.

          Rule Details

          This rule enforces parentheses around arrow function parameters regardless of arity. For example:

          /*eslint-env es6*/
          
          // Bad
          a => {}
          
          // Good
          (a) => {}

          Following this style will help you find arrow functions (=>) which may be mistakenly included in a condition when a comparison such as >= was the intent.

          /*eslint-env es6*/
          
          // Bad
          if (a => 2) {
          }
          
          // Good
          if (a >= 2) {
          }

          The rule can also be configured to discourage the use of parens when they are not required:

          /*eslint-env es6*/
          
          // Bad
          (a) => {}
          
          // Good
          a => {}

          Options

          This rule has a string option and an object one.

          String options are:

          • "always" (default) requires parens around arguments in all cases.
          • "as-needed" allows omitting parens when there is only one argument.

          Object properties for variants of the "as-needed" option:

          • "requireForBlockBody": true modifies the as-needed rule in order to require parens if the function body is in an instructions block (surrounded by braces).

          always

          Examples of incorrect code for this rule with the default "always" option:

          /*eslint arrow-parens: ["error", "always"]*/
          /*eslint-env es6*/
          
          a => {};
          a => a;
          a => {'\n'};
          a.then(foo => {});
          a.then(foo => a);
          a(foo => { if (true) {} });

          Examples of correct code for this rule with the default "always" option:

          /*eslint arrow-parens: ["error", "always"]*/
          /*eslint-env es6*/
          
          () => {};
          (a) => {};
          (a) => a;
          (a) => {'\n'}
          a.then((foo) => {});
          a.then((foo) => { if (true) {} });

          If Statements

          One of benefits of this option is that it prevents the incorrect use of arrow functions in conditionals:

          /*eslint-env es6*/
          
          var a = 1;
          var b = 2;
          // ...
          if (a => b) {
           console.log('bigger');
          } else {
           console.log('smaller');
          }
          // outputs 'bigger', not smaller as expected

          The contents of the if statement is an arrow function, not a comparison.

          If the arrow function is intentional, it should be wrapped in parens to remove ambiguity.

          /*eslint-env es6*/
          
          var a = 1;
          var b = 0;
          // ...
          if ((a) => b) {
           console.log('truthy value returned');
          } else {
           console.log('falsey value returned');
          }
          // outputs 'truthy value returned'

          The following is another example of this behavior:

          /*eslint-env es6*/
          
          var a = 1, b = 2, c = 3, d = 4;
          var f = a => b ? c: d;
          // f = ?

          f is an arrow function which takes a as an argument and returns the result of b ? c: d.

          This should be rewritten like so:

          /*eslint-env es6*/
          
          var a = 1, b = 2, c = 3, d = 4;
          var f = (a) => b ? c: d;

          as-needed

          Examples of incorrect code for this rule with the "as-needed" option:

          /*eslint arrow-parens: ["error", "as-needed"]*/
          /*eslint-env es6*/
          
          (a) => {};
          (a) => a;
          (a) => {'\n'};
          a.then((foo) => {});
          a.then((foo) => a);
          a((foo) => { if (true) {} });

          Examples of correct code for this rule with the "as-needed" option:

          /*eslint arrow-parens: ["error", "as-needed"]*/
          /*eslint-env es6*/
          
          () => {};
          a => {};
          a => a;
          a => {'\n'};
          a.then(foo => {});
          a.then(foo => { if (true) {} });
          (a, b, c) => a;
          (a = 10) => a;
          ([a, b]) => a;
          ({a, b}) => a;

          requireForBlockBody

          Examples of incorrect code for the { "requireForBlockBody": true } option:

          /*eslint arrow-parens: [2, "as-needed", { "requireForBlockBody": true }]*/
          /*eslint-env es6*/
          
          (a) => a;
          a => {};
          a => {'\n'};
          a.map((x) => x * x);
          a.map(x => {
            return x * x;
          });
          a.then(foo => {});

          Examples of correct code for the { "requireForBlockBody": true } option:

          /*eslint arrow-parens: [2, "as-needed", { "requireForBlockBody": true }]*/
          /*eslint-env es6*/
          
          (a) => {};
          (a) => {'\n'};
          a => ({});
          () => {};
          a => a;
          a.then((foo) => {});
          a.then((foo) => { if (true) {} });
          a((foo) => { if (true) {} });
          (a, b, c) => a;
          (a = 10) => a;
          ([a, b]) => a;
          ({a, b}) => a;

          Further Reading

          Missing trailing comma.
          Open

                })
          Severity: Minor
          Found in src/server/token/issue.js by eslint

          require or disallow trailing commas (comma-dangle)

          Trailing commas in object literals are valid according to the ECMAScript 5 (and ECMAScript 3!) spec. However, IE8 (when not in IE8 document mode) and below will throw an error when it encounters trailing commas in JavaScript.

          var foo = {
              bar: "baz",
              qux: "quux",
          };

          Trailing commas simplify adding and removing items to objects and arrays, since only the lines you are modifying must be touched. Another argument in favor of trailing commas is that it improves the clarity of diffs when an item is added or removed from an object or array:

          Less clear:

          var foo = {
          -    bar: "baz",
          -    qux: "quux"
          +    bar: "baz"
           };

          More clear:

          var foo = {
               bar: "baz",
          -    qux: "quux",
           };

          Rule Details

          This rule enforces consistent use of trailing commas in object and array literals.

          Options

          This rule has a string option or an object option:

          {
              "comma-dangle": ["error", "never"],
              // or
              "comma-dangle": ["error", {
                  "arrays": "never",
                  "objects": "never",
                  "imports": "never",
                  "exports": "never",
                  "functions": "ignore",
              }]
          }
          • "never" (default) disallows trailing commas
          • "always" requires trailing commas
          • "always-multiline" requires trailing commas when the last element or property is in a different line than the closing ] or } and disallows trailing commas when the last element or property is on the same line as the closing ] or }
          • "only-multiline" allows (but does not require) trailing commas when the last element or property is in a different line than the closing ] or } and disallows trailing commas when the last element or property is on the same line as the closing ] or }

          Trailing commas in function declarations and function calls are valid syntax since ECMAScript 2017; however, the string option does not check these situations for backwards compatibility.

          You can also use an object option to configure this rule for each type of syntax. Each of the following options can be set to "never", "always", "always-multiline", "only-multiline", or "ignore". The default for each option is "never" unless otherwise specified.

          • arrays is for array literals and array patterns of destructuring. (e.g. let [a,] = [1,];)
          • objects is for object literals and object patterns of destructuring. (e.g. let {a,} = {a: 1};)
          • imports is for import declarations of ES Modules. (e.g. import {a,} from "foo";)
          • exports is for export declarations of ES Modules. (e.g. export {a,};)
          • functions is for function declarations and function calls. (e.g. (function(a,){ })(b,);)
            functions is set to "ignore" by default for consistency with the string option.

          never

          Examples of incorrect code for this rule with the default "never" option:

          /*eslint comma-dangle: ["error", "never"]*/
          
          var foo = {
              bar: "baz",
              qux: "quux",
          };
          
          var arr = [1,2,];
          
          foo({
            bar: "baz",
            qux: "quux",
          });

          Examples of correct code for this rule with the default "never" option:

          /*eslint comma-dangle: ["error", "never"]*/
          
          var foo = {
              bar: "baz",
              qux: "quux"
          };
          
          var arr = [1,2];
          
          foo({
            bar: "baz",
            qux: "quux"
          });

          always

          Examples of incorrect code for this rule with the "always" option:

          /*eslint comma-dangle: ["error", "always"]*/
          
          var foo = {
              bar: "baz",
              qux: "quux"
          };
          
          var arr = [1,2];
          
          foo({
            bar: "baz",
            qux: "quux"
          });

          Examples of correct code for this rule with the "always" option:

          /*eslint comma-dangle: ["error", "always"]*/
          
          var foo = {
              bar: "baz",
              qux: "quux",
          };
          
          var arr = [1,2,];
          
          foo({
            bar: "baz",
            qux: "quux",
          });

          always-multiline

          Examples of incorrect code for this rule with the "always-multiline" option:

          /*eslint comma-dangle: ["error", "always-multiline"]*/
          
          var foo = {
              bar: "baz",
              qux: "quux"
          };
          
          var foo = { bar: "baz", qux: "quux", };
          
          var arr = [1,2,];
          
          var arr = [1,
              2,];
          
          var arr = [
              1,
              2
          ];
          
          foo({
            bar: "baz",
            qux: "quux"
          });

          Examples of correct code for this rule with the "always-multiline" option:

          /*eslint comma-dangle: ["error", "always-multiline"]*/
          
          var foo = {
              bar: "baz",
              qux: "quux",
          };
          
          var foo = {bar: "baz", qux: "quux"};
          var arr = [1,2];
          
          var arr = [1,
              2];
          
          var arr = [
              1,
              2,
          ];
          
          foo({
            bar: "baz",
            qux: "quux",
          });

          only-multiline

          Examples of incorrect code for this rule with the "only-multiline" option:

          /*eslint comma-dangle: ["error", "only-multiline"]*/
          
          var foo = { bar: "baz", qux: "quux", };
          
          var arr = [1,2,];
          
          var arr = [1,
              2,];

          Examples of correct code for this rule with the "only-multiline" option:

          /*eslint comma-dangle: ["error", "only-multiline"]*/
          
          var foo = {
              bar: "baz",
              qux: "quux",
          };
          
          var foo = {
              bar: "baz",
              qux: "quux"
          };
          
          var foo = {bar: "baz", qux: "quux"};
          var arr = [1,2];
          
          var arr = [1,
              2];
          
          var arr = [
              1,
              2,
          ];
          
          var arr = [
              1,
              2
          ];
          
          foo({
            bar: "baz",
            qux: "quux",
          });
          
          foo({
            bar: "baz",
            qux: "quux"
          });

          functions

          Examples of incorrect code for this rule with the {"functions": "never"} option:

          /*eslint comma-dangle: ["error", {"functions": "never"}]*/
          
          function foo(a, b,) {
          }
          
          foo(a, b,);
          new foo(a, b,);

          Examples of correct code for this rule with the {"functions": "never"} option:

          /*eslint comma-dangle: ["error", {"functions": "never"}]*/
          
          function foo(a, b) {
          }
          
          foo(a, b);
          new foo(a, b);

          Examples of incorrect code for this rule with the {"functions": "always"} option:

          /*eslint comma-dangle: ["error", {"functions": "always"}]*/
          
          function foo(a, b) {
          }
          
          foo(a, b);
          new foo(a, b);

          Examples of correct code for this rule with the {"functions": "always"} option:

          /*eslint comma-dangle: ["error", {"functions": "always"}]*/
          
          function foo(a, b,) {
          }
          
          foo(a, b,);
          new foo(a, b,);

          When Not To Use It

          You can turn this rule off if you are not concerned with dangling commas. Source: http://eslint.org/docs/rules/

          Severity
          Category
          Status
          Source
          Language