Require space before/after arrow function's arrow (arrow-spacing)

This rule normalize style of spacing before/after an arrow function's arrow(=>).

/*eslint-env es6*/

// { "before": true, "after": true }
(a) => {}

// { "before": false, "after": false }
(a)=>{}

Rule Details

This rule takes an object argument with before and after properties, each with a Boolean value.

The default configuration is { "before": true, "after": true }.

true means there should be one or more spaces and false means no spaces.

Examples of incorrect code for this rule with the default { "before": true, "after": true } option:

/*eslint arrow-spacing: "error"*/
/*eslint-env es6*/

()=> {};
() =>{};
(a)=> {};
(a) =>{};
a =>a;
a=> a;
()=> {'\n'};
() =>{'\n'};

Examples of correct code for this rule with the default { "before": true, "after": true } option:

/*eslint arrow-spacing: "error"*/
/*eslint-env es6*/

() => {};
(a) => {};
a => a;
() => {'\n'};

Examples of incorrect code for this rule with the { "before": false, "after": false } option:

/*eslint arrow-spacing: ["error", { "before": false, "after": false }]*/
/*eslint-env es6*/

() =>{};
(a) => {};
()=> {'\n'};

Examples of correct code for this rule with the { "before": false, "after": false } option:

/*eslint arrow-spacing: ["error", { "before": false, "after": false }]*/
/*eslint-env es6*/

()=>{};
(a)=>{};
()=>{'\n'};

Examples of incorrect code for this rule with the { "before": false, "after": true } option:

/*eslint arrow-spacing: ["error", { "before": false, "after": true }]*/
/*eslint-env es6*/

() =>{};
(a) => {};
()=>{'\n'};

Examples of correct code for this rule with the { "before": false, "after": true } option:

/*eslint arrow-spacing: ["error", { "before": false, "after": true }]*/
/*eslint-env es6*/

()=> {};
(a)=> {};
()=> {'\n'};

Source: http://eslint.org/docs/rules/

Disallow unnecessary constructor (no-useless-constructor)

ES2015 provides a default class constructor if one is not specified. As such, it is unnecessary to provide an empty constructor or one that simply delegates into its parent class, as in the following examples:

class A {
    constructor () {
    }
}

class A extends B {
    constructor (value) {
      super(value);
    }
}

Rule Details

This rule flags class constructors that can be safely removed without changing how the class works.

Examples

Examples of incorrect code for this rule:

/*eslint no-useless-constructor: "error"*/
/*eslint-env es6*/

class A {
    constructor () {
    }
}

class A extends B {
    constructor (...args) {
      super(...args);
    }
}

Examples of correct code for this rule:

/*eslint no-useless-constructor: "error"*/

class A { }

class A {
    constructor () {
        doSomething();
    }
}

class A extends B {
    constructor() {
        super('foo');
    }
}

class A extends B {
    constructor() {
        super();
        doSomething();
    }
}

When Not To Use It

If you don't want to be notified about unnecessary constructors, you can safely disable this rule. Source: http://eslint.org/docs/rules/

Require space before/after arrow function's arrow (arrow-spacing)

This rule normalize style of spacing before/after an arrow function's arrow(=>).

/*eslint-env es6*/

// { "before": true, "after": true }
(a) => {}

// { "before": false, "after": false }
(a)=>{}

Rule Details

This rule takes an object argument with before and after properties, each with a Boolean value.

The default configuration is { "before": true, "after": true }.

true means there should be one or more spaces and false means no spaces.

Examples of incorrect code for this rule with the default { "before": true, "after": true } option:

/*eslint arrow-spacing: "error"*/
/*eslint-env es6*/

()=> {};
() =>{};
(a)=> {};
(a) =>{};
a =>a;
a=> a;
()=> {'\n'};
() =>{'\n'};

Examples of correct code for this rule with the default { "before": true, "after": true } option:

/*eslint arrow-spacing: "error"*/
/*eslint-env es6*/

() => {};
(a) => {};
a => a;
() => {'\n'};

Examples of incorrect code for this rule with the { "before": false, "after": false } option:

/*eslint arrow-spacing: ["error", { "before": false, "after": false }]*/
/*eslint-env es6*/

() =>{};
(a) => {};
()=> {'\n'};

Examples of correct code for this rule with the { "before": false, "after": false } option:

/*eslint arrow-spacing: ["error", { "before": false, "after": false }]*/
/*eslint-env es6*/

()=>{};
(a)=>{};
()=>{'\n'};

Examples of incorrect code for this rule with the { "before": false, "after": true } option:

/*eslint arrow-spacing: ["error", { "before": false, "after": true }]*/
/*eslint-env es6*/

() =>{};
(a) => {};
()=>{'\n'};

Examples of correct code for this rule with the { "before": false, "after": true } option:

/*eslint arrow-spacing: ["error", { "before": false, "after": true }]*/
/*eslint-env es6*/

()=> {};
(a)=> {};
()=> {'\n'};

Source: http://eslint.org/docs/rules/

Require braces in arrow function body (arrow-body-style)

Arrow functions have two syntactic forms for their function bodies. They may be defined with a block body (denoted by curly braces) () => { ... } or with a single expression () => ..., whose value is implicitly returned.

Rule Details

This rule can enforce or disallow the use of braces around arrow function body.

Options

The rule takes one or two options. The first is a string, which can be:

• "always" enforces braces around the function body
• "as-needed" enforces no braces where they can be omitted (default)
• "never" enforces no braces around the function body (constrains arrow functions to the role of returning an expression)

The second one is an object for more fine-grained configuration when the first option is "as-needed". Currently, the only available option is requireReturnForObjectLiteral, a boolean property. It's false by default. If set to true, it requires braces and an explicit return for object literals.

"arrow-body-style": ["error", "always"]

always

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

/*eslint arrow-body-style: ["error", "always"]*/
/*eslint-env es6*/
let foo = () => 0;

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

let foo = () => {
    return 0;
};
let foo = (retv, name) => {
    retv[name] = true;
    return retv;
};

as-needed

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

/*eslint arrow-body-style: ["error", "as-needed"]*/
/*eslint-env es6*/

let foo = () => {
    return 0;
};
let foo = () => {
    return {
       bar: {
            foo: 1,
            bar: 2,
        }
    };
};

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

/*eslint arrow-body-style: ["error", "as-needed"]*/
/*eslint-env es6*/

let foo = () => 0;
let foo = (retv, name) => {
    retv[name] = true;
    return retv;
};
let foo = () => ({
    bar: {
        foo: 1,
        bar: 2,
    }
});
let foo = () => { bar(); };
let foo = () => {};
let foo = () => { /* do nothing */ };
let foo = () => {
    // do nothing.
};
let foo = () => ({ bar: 0 });

requireReturnForObjectLiteral

This option is only applicable when used in conjunction with the "as-needed" option.

Examples of incorrect code for this rule with the { "requireReturnForObjectLiteral": true } option:

/*eslint arrow-body-style: ["error", "as-needed", { "requireReturnForObjectLiteral": true }]*/
/*eslint-env es6*/
let foo = () => ({});
let foo = () => ({ bar: 0 });

Examples of correct code for this rule with the { "requireReturnForObjectLiteral": true } option:

/*eslint arrow-body-style: ["error", "as-needed", { "requireReturnForObjectLiteral": true }]*/
/*eslint-env es6*/

let foo = () => {};
let foo = () => { return { bar: 0 }; };

never

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

/*eslint arrow-body-style: ["error", "never"]*/
/*eslint-env es6*/

let foo = () => {
    return 0;
};
let foo = (retv, name) => {
    retv[name] = true;
    return retv;
};

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

/*eslint arrow-body-style: ["error", "never"]*/
/*eslint-env es6*/

let foo = () => 0;
let foo = () => ({ foo: 0 });

Source: http://eslint.org/docs/rules/

Require space before/after arrow function's arrow (arrow-spacing)

This rule normalize style of spacing before/after an arrow function's arrow(=>).

/*eslint-env es6*/

// { "before": true, "after": true }
(a) => {}

// { "before": false, "after": false }
(a)=>{}

Rule Details

This rule takes an object argument with before and after properties, each with a Boolean value.

The default configuration is { "before": true, "after": true }.

true means there should be one or more spaces and false means no spaces.

Examples of incorrect code for this rule with the default { "before": true, "after": true } option:

/*eslint arrow-spacing: "error"*/
/*eslint-env es6*/

()=> {};
() =>{};
(a)=> {};
(a) =>{};
a =>a;
a=> a;
()=> {'\n'};
() =>{'\n'};

Examples of correct code for this rule with the default { "before": true, "after": true } option:

/*eslint arrow-spacing: "error"*/
/*eslint-env es6*/

() => {};
(a) => {};
a => a;
() => {'\n'};

Examples of incorrect code for this rule with the { "before": false, "after": false } option:

/*eslint arrow-spacing: ["error", { "before": false, "after": false }]*/
/*eslint-env es6*/

() =>{};
(a) => {};
()=> {'\n'};

Examples of correct code for this rule with the { "before": false, "after": false } option:

/*eslint arrow-spacing: ["error", { "before": false, "after": false }]*/
/*eslint-env es6*/

()=>{};
(a)=>{};
()=>{'\n'};

Examples of incorrect code for this rule with the { "before": false, "after": true } option:

/*eslint arrow-spacing: ["error", { "before": false, "after": true }]*/
/*eslint-env es6*/

() =>{};
(a) => {};
()=>{'\n'};

Examples of correct code for this rule with the { "before": false, "after": true } option:

/*eslint arrow-spacing: ["error", { "before": false, "after": true }]*/
/*eslint-env es6*/

()=> {};
(a)=> {};
()=> {'\n'};

Source: http://eslint.org/docs/rules/

Require space before/after arrow function's arrow (arrow-spacing)

This rule normalize style of spacing before/after an arrow function's arrow(=>).

/*eslint-env es6*/

// { "before": true, "after": true }
(a) => {}

// { "before": false, "after": false }
(a)=>{}

Rule Details

This rule takes an object argument with before and after properties, each with a Boolean value.

The default configuration is { "before": true, "after": true }.

true means there should be one or more spaces and false means no spaces.

Examples of incorrect code for this rule with the default { "before": true, "after": true } option:

/*eslint arrow-spacing: "error"*/
/*eslint-env es6*/

()=> {};
() =>{};
(a)=> {};
(a) =>{};
a =>a;
a=> a;
()=> {'\n'};
() =>{'\n'};

Examples of correct code for this rule with the default { "before": true, "after": true } option:

/*eslint arrow-spacing: "error"*/
/*eslint-env es6*/

() => {};
(a) => {};
a => a;
() => {'\n'};

Examples of incorrect code for this rule with the { "before": false, "after": false } option:

/*eslint arrow-spacing: ["error", { "before": false, "after": false }]*/
/*eslint-env es6*/

() =>{};
(a) => {};
()=> {'\n'};

Examples of correct code for this rule with the { "before": false, "after": false } option:

/*eslint arrow-spacing: ["error", { "before": false, "after": false }]*/
/*eslint-env es6*/

()=>{};
(a)=>{};
()=>{'\n'};

Examples of incorrect code for this rule with the { "before": false, "after": true } option:

/*eslint arrow-spacing: ["error", { "before": false, "after": true }]*/
/*eslint-env es6*/

() =>{};
(a) => {};
()=>{'\n'};

Examples of correct code for this rule with the { "before": false, "after": true } option:

/*eslint arrow-spacing: ["error", { "before": false, "after": true }]*/
/*eslint-env es6*/

()=> {};
(a)=> {};
()=> {'\n'};

Source: http://eslint.org/docs/rules/

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 57.

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

• Extract Method
• Extract Class
• Form Template Method
• Introduce Null Object
• Pull Up Method
• Pull Up Field
• Substitute Algorithm

Further Reading

• Don't Repeat Yourself on the C2 Wiki
• Duplicated Code on SourceMaking
• Refactoring: Improving the Design of Existing Code by Martin Fowler. Duplicated Code, p76

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 57.

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

• Extract Method
• Extract Class
• Form Template Method
• Introduce Null Object
• Pull Up Method
• Pull Up Field
• Substitute Algorithm

Further Reading

• Don't Repeat Yourself on the C2 Wiki
• Duplicated Code on SourceMaking
• Refactoring: Improving the Design of Existing Code by Martin Fowler. Duplicated Code, p76

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 57.

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

• Extract Method
• Extract Class
• Form Template Method
• Introduce Null Object
• Pull Up Method
• Pull Up Field
• Substitute Algorithm

Further Reading

• Don't Repeat Yourself on the C2 Wiki
• Duplicated Code on SourceMaking
• Refactoring: Improving the Design of Existing Code by Martin Fowler. Duplicated Code, p76

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 57.

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

• Extract Method
• Extract Class
• Form Template Method
• Introduce Null Object
• Pull Up Method
• Pull Up Field
• Substitute Algorithm

Further Reading

• Don't Repeat Yourself on the C2 Wiki
• Duplicated Code on SourceMaking
• Refactoring: Improving the Design of Existing Code by Martin Fowler. Duplicated Code, p76

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 45.

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

• Extract Method
• Extract Class
• Form Template Method
• Introduce Null Object
• Pull Up Method
• Pull Up Field
• Substitute Algorithm

Further Reading

• Don't Repeat Yourself on the C2 Wiki
• Duplicated Code on SourceMaking
• Refactoring: Improving the Design of Existing Code by Martin Fowler. Duplicated Code, p76

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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