if (!profile.balloonname) {
                  if (balloon_result) {
                    // 同梱バルーンを初期設定
                    profile.balloonname = balloon_result.directory;
                  } else {

Close

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 54.

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

  _load_shell(directory, GhostViewClass = this.GhostViewClass) {
    const shell = new GhostViewClass.Shell(directory.asArrayBuffer());
    return shell.load();
  }

Close

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 54.

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

  _load_balloon(directory, GhostViewClass = this.GhostViewClass) {
    const balloon = new GhostViewClass.Balloon(directory.asArrayBuffer());
    return balloon.load();
  }

Close

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 54.

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

      install_results.forEach((install_result) => {
        if (install_result.type === 'ghost') {
          ghost_result = install_result;
        } else if (install_result.type === 'balloon') {
          balloon_result = install_result;

Close

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 49.

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

                install_results.forEach(function (install_result) {
                  if (install_result.type === 'ghost') {
                    ghost_result = install_result;
                  } else if (install_result.type === 'balloon') {
                    balloon_result = install_result;

Close

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 49.

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

    value: function _canondirpath(dirpath) {
      var path_separator = dirpath.match(/[\\\/]/)[0];
      return dirpath.replace(new RegExp('\\' + path_separator + '?$'), path_separator);
    }

Close

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 47.

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

  _canondirpath(dirpath) {
    const path_separator = dirpath.match(/[\\\/]/)[0];
    return dirpath.replace(
      new RegExp('\\' + path_separator + '?$'),
      path_separator

Close

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 47.

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

export default function mixinClass(baseClass, target){
    const targetObj = (typeof(target) === "function")
                      ? target.prototype
                      : target;

Close

Cognitive Complexity

Cognitive Complexity is a measure of how difficult a unit of code is to intuitively understand. Unlike Cyclomatic Complexity, which determines how difficult your code will be to test, Cognitive Complexity tells you how difficult your code will be to read and comprehend.

A method's cognitive complexity is based on a few simple rules:

• Code is not considered more complex when it uses shorthand that the language provides for collapsing multiple statements into one
• Code is considered more complex for each "break in the linear flow of the code"
• Code is considered more complex when "flow breaking structures are nested"

Further reading

• Cognitive Complexity docs
• Cognitive Complexity: A new way of measuring understandability

import package_json from './package.json';

Close

Disallow Unused Variables (no-unused-vars)

Variables that are declared and not used anywhere in the code are most likely an error due to incomplete refactoring. Such variables take up space in the code and can lead to confusion by readers.

Rule Details

This rule is aimed at eliminating unused variables, functions, and parameters of functions.

A variable is considered to be used if any of the following are true:

• It represents a function that is called (doSomething())
• It is read (var y = x)
• It is passed into a function as an argument (doSomething(x))
• It is read inside of a function that is passed to another function (doSomething(function() { foo(); }))

A variable is not considered to be used if it is only ever assigned to (var x = 5) or declared.

Examples of incorrect code for this rule:

/*eslint no-unused-vars: "error"*/
/*global some_unused_var*/

// It checks variables you have defined as global
some_unused_var = 42;

var x;

// Write-only variables are not considered as used.
var y = 10;
y = 5;

// A read for a modification of itself is not considered as used.
var z = 0;
z = z + 1;

// By default, unused arguments cause warnings.
(function(foo) {
    return 5;
})();

// Unused recursive functions also cause warnings.
function fact(n) {
    if (n < 2) return 1;
    return n * fact(n - 1);
}

// When a function definition destructures an array, unused entries from the array also cause warnings.
function getY([x, y]) {
    return y;
}

Examples of correct code for this rule:

/*eslint no-unused-vars: "error"*/

var x = 10;
alert(x);

// foo is considered used here
myFunc(function foo() {
    // ...
}.bind(this));

(function(foo) {
    return foo;
})();

var myFunc;
myFunc = setTimeout(function() {
    // myFunc is considered used
    myFunc();
}, 50);

// Only the second argument from the descructured array is used.
function getY([, y]) {
    return y;
}

exported

In environments outside of CommonJS or ECMAScript modules, you may use var to create a global variable that may be used by other scripts. You can use the /* exported variableName */ comment block to indicate that this variable is being exported and therefore should not be considered unused.

Note that /* exported */ has no effect for any of the following:

• when the environment is node or commonjs
• when parserOptions.sourceType is module
• when ecmaFeatures.globalReturn is true

The line comment // exported variableName will not work as exported is not line-specific.

Examples of correct code for /* exported variableName */ operation:

/* exported global_var */

var global_var = 42;

Options

This rule takes one argument which can be a string or an object. The string settings are the same as those of the vars property (explained below).

By default this rule is enabled with all option for variables and after-used for arguments.

{
    "rules": {
        "no-unused-vars": ["error", { "vars": "all", "args": "after-used", "ignoreRestSiblings": false }]
    }
}

vars

The vars option has two settings:

• all checks all variables for usage, including those in the global scope. This is the default setting.
• local checks only that locally-declared variables are used but will allow global variables to be unused.

vars: local

Examples of correct code for the { "vars": "local" } option:

/*eslint no-unused-vars: ["error", { "vars": "local" }]*/
/*global some_unused_var */

some_unused_var = 42;

varsIgnorePattern

The varsIgnorePattern option specifies exceptions not to check for usage: variables whose names match a regexp pattern. For example, variables whose names contain ignored or Ignored.

Examples of correct code for the { "varsIgnorePattern": "[iI]gnored" } option:

/*eslint no-unused-vars: ["error", { "varsIgnorePattern": "[iI]gnored" }]*/

var firstVarIgnored = 1;
var secondVar = 2;
console.log(secondVar);

args

The args option has three settings:

• after-used - only the last argument must be used. This allows you, for instance, to have two named parameters to a function and as long as you use the second argument, ESLint will not warn you about the first. This is the default setting.
• all - all named arguments must be used.
• none - do not check arguments.

args: after-used

Examples of incorrect code for the default { "args": "after-used" } option:

/*eslint no-unused-vars: ["error", { "args": "after-used" }]*/

// 1 error
// "baz" is defined but never used
(function(foo, bar, baz) {
    return bar;
})();

Examples of correct code for the default { "args": "after-used" } option:

/*eslint no-unused-vars: ["error", {"args": "after-used"}]*/

(function(foo, bar, baz) {
    return baz;
})();

args: all

Examples of incorrect code for the { "args": "all" } option:

/*eslint no-unused-vars: ["error", { "args": "all" }]*/

// 2 errors
// "foo" is defined but never used
// "baz" is defined but never used
(function(foo, bar, baz) {
    return bar;
})();

args: none

Examples of correct code for the { "args": "none" } option:

/*eslint no-unused-vars: ["error", { "args": "none" }]*/

(function(foo, bar, baz) {
    return bar;
})();

ignoreRestSiblings

The ignoreRestSiblings option is a boolean (default: false). Using a Rest Property it is possible to "omit" properties from an object, but by default the sibling properties are marked as "unused". With this option enabled the rest property's siblings are ignored.

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

/*eslint no-unused-vars: ["error", { "ignoreRestSiblings": true }]*/
// 'type' is ignored because it has a rest property sibling.
var { type, ...coords } = data;

argsIgnorePattern

The argsIgnorePattern option specifies exceptions not to check for usage: arguments whose names match a regexp pattern. For example, variables whose names begin with an underscore.

Examples of correct code for the { "argsIgnorePattern": "^_" } option:

/*eslint no-unused-vars: ["error", { "argsIgnorePattern": "^_" }]*/

function foo(x, _y) {
    return x + 1;
}
foo();

caughtErrors

The caughtErrors option is used for catch block arguments validation.

It has two settings:

• none - do not check error objects. This is the default setting.
• all - all named arguments must be used.

caughtErrors: none

Not specifying this rule is equivalent of assigning it to none.

Examples of correct code for the { "caughtErrors": "none" } option:

/*eslint no-unused-vars: ["error", { "caughtErrors": "none" }]*/

try {
    //...
} catch (err) {
    console.error("errors");
}

caughtErrors: all

Examples of incorrect code for the { "caughtErrors": "all" } option:

/*eslint no-unused-vars: ["error", { "caughtErrors": "all" }]*/

// 1 error
// "err" is defined but never used
try {
    //...
} catch (err) {
    console.error("errors");
}

caughtErrorsIgnorePattern

The caughtErrorsIgnorePattern option specifies exceptions not to check for usage: catch arguments whose names match a regexp pattern. For example, variables whose names begin with a string 'ignore'.

Examples of correct code for the { "caughtErrorsIgnorePattern": "^ignore" } option:

/*eslint no-unused-vars: ["error", { "caughtErrorsIgnorePattern": "^ignore" }]*/

try {
    //...
} catch (ignoreErr) {
    console.error("errors");
}

When Not To Use It

If you don't want to be notified about unused variables or function arguments, you can safely turn this rule off. Source: http://eslint.org/docs/rules/

  return $.notify.onError({ title: title, message: 'Error: <%= error.message %>', sound: sound });

Close

Require Object Literal Shorthand Syntax (object-shorthand)

EcmaScript 6 provides a concise form for defining object literal methods and properties. This syntax can make defining complex object literals much cleaner.

Here are a few common examples using the ES5 syntax:

// properties
var foo = {
    x: x,
    y: y,
    z: z,
};

// methods
var foo = {
    a: function() {},
    b: function() {}
};

Now here are ES6 equivalents:

/*eslint-env es6*/

// properties
var foo = {x, y, z};

// methods
var foo = {
    a() {},
    b() {}
};

Rule Details

This rule enforces the use of the shorthand syntax. This applies to all methods (including generators) defined in object literals and any properties defined where the key name matches name of the assigned variable.

Each of the following properties would warn:

/*eslint object-shorthand: "error"*/
/*eslint-env es6*/

var foo = {
    w: function() {},
    x: function *() {},
    [y]: function() {},
    z: z
};

In that case the expected syntax would have been:

/*eslint object-shorthand: "error"*/
/*eslint-env es6*/

var foo = {
    w() {},
    *x() {},
    [y]() {},
    z
};

This rule does not flag arrow functions inside of object literals. The following will not warn:

/*eslint object-shorthand: "error"*/
/*eslint-env es6*/

var foo = {
    x: (y) => y
};

Options

The rule takes an option which specifies when it should be applied. It can be set to one of the following values:

• "always" (default) expects that the shorthand will be used whenever possible.
• "methods" ensures the method shorthand is used (also applies to generators).
• "properties" ensures the property shorthand is used (where the key and variable name match).
• "never" ensures that no property or method shorthand is used in any object literal.
• "consistent" ensures that either all shorthand or all longform will be used in an object literal.
• "consistent-as-needed" ensures that either all shorthand or all longform will be used in an object literal, but ensures all shorthand whenever possible.

You can set the option in configuration like this:

{
    "object-shorthand": ["error", "always"]
}

Additionally, the rule takes an optional object configuration:

• "avoidQuotes": true indicates that longform syntax is preferred whenever the object key is a string literal (default: false). Note that this option can only be enabled when the string option is set to "always", "methods", or "properties".
• "ignoreConstructors": true can be used to prevent the rule from reporting errors for constructor functions. (By default, the rule treats constructors the same way as other functions.) Note that this option can only be enabled when the string option is set to "always" or "methods".
• "avoidExplicitReturnArrows": true indicates that methods are preferred over explicit-return arrow functions for function properties. (By default, the rule allows either of these.) Note that this option can only be enabled when the string option is set to "always" or "methods".

avoidQuotes

{
    "object-shorthand": ["error", "always", { "avoidQuotes": true }]
}

Example of incorrect code for this rule with the "always", { "avoidQuotes": true } option:

/*eslint object-shorthand: ["error", "always", { "avoidQuotes": true }]*/
/*eslint-env es6*/

var foo = {
    "bar-baz"() {}
};

Example of correct code for this rule with the "always", { "avoidQuotes": true } option:

/*eslint object-shorthand: ["error", "always", { "avoidQuotes": true }]*/
/*eslint-env es6*/

var foo = {
    "bar-baz": function() {},
    "qux": qux
};

ignoreConstructors

{
    "object-shorthand": ["error", "always", { "ignoreConstructors": true }]
}

Example of correct code for this rule with the "always", { "ignoreConstructors": true } option:

/*eslint object-shorthand: ["error", "always", { "ignoreConstructors": true }]*/
/*eslint-env es6*/

var foo = {
    ConstructorFunction: function() {}
};

avoidExplicitReturnArrows

{
    "object-shorthand": ["error", "always", { "avoidExplicitReturnArrows": true }]
}

Example of incorrect code for this rule with the "always", { "avoidExplicitReturnArrows": true } option:

/*eslint object-shorthand: ["error", "always", { "avoidExplicitReturnArrows": true }]*/
/*eslint-env es6*/

var foo = {
  foo: (bar, baz) => {
    return bar + baz;
  },

  qux: (foobar) => {
    return foobar * 2;
  }
};

Example of correct code for this rule with the "always", { "avoidExplicitReturnArrows": true } option:

/*eslint object-shorthand: ["error", "always", { "avoidExplicitReturnArrows": true }]*/
/*eslint-env es6*/

var foo = {
  foo(bar, baz) {
    return bar + baz;
  },

  qux: foobar => foobar * 2
};

Example of incorrect code for this rule with the "consistent" option:

/*eslint object-shorthand: [2, "consistent"]*/
/*eslint-env es6*/

var foo = {
    a,
    b: "foo",
};

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

/*eslint object-shorthand: [2, "consistent"]*/
/*eslint-env es6*/

var foo = {
    a: a,
    b: "foo"
};

var bar = {
    a,
    b,
};

Example of incorrect code with the "consistent-as-needed" option, which is very similar to "consistent":

/*eslint object-shorthand: [2, "consistent-as-needed"]*/
/*eslint-env es6*/

var foo = {
    a: a,
    b: b,
};

When Not To Use It

Anyone not yet in an ES6 environment would not want to apply this rule. Others may find the terseness of the shorthand syntax harder to read and may not want to encourage it with this rule.

Further Reading

Object initializer - MDN Source: http://eslint.org/docs/rules/

gulp.task('pre-test', function() {

Close

Suggest using arrow functions as callbacks. (prefer-arrow-callback)

Arrow functions are suited to callbacks, because:

• this keywords in arrow functions bind to the upper scope's.
• The notation of the arrow function is shorter than function expression's.

Rule Details

This rule is aimed to flag usage of function expressions in an argument list.

The following patterns are considered problems:

/*eslint prefer-arrow-callback: "error"*/

foo(function(a) { return a; });
foo(function() { return this.a; }.bind(this));

The following patterns are not considered problems:

/*eslint prefer-arrow-callback: "error"*/
/*eslint-env es6*/

foo(a => a);
foo(function*() { yield; });

// this is not a callback.
var foo = function foo(a) { return a; };

// using `this` without `.bind(this)`.
foo(function() { return this.a; });

// recursively.
foo(function bar(n) { return n && n + bar(n - 1); });

Options

This rule takes one optional argument, an object which is an options object.

allowNamedFunctions

This is a boolean option and it is false by default. When set to true, the rule doesn't warn on named functions used as callbacks.

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

/*eslint prefer-arrow-callback: ["error", { "allowNamedFunctions": true }]*/

foo(function bar() {});

allowUnboundThis

This is a boolean option and it is true by default. When set to false, this option allows the use of this without restriction and checks for dynamically assigned this values such as when using Array.prototype.map with a context argument. Normally, the rule will flag the use of this whenever a function does not use bind() to specify the value of this constantly.

Examples of incorrect code for the { "allowUnboundThis": false } option:

/*eslint prefer-arrow-callback: ["error", { "allowUnboundThis": false }]*/
/*eslint-env es6*/

foo(function() { this.a; });

foo(function() { (() => this); });

someArray.map(function (itm) { return this.doSomething(itm); }, someObject);

When Not To Use It

This rule should not be used in ES3/5 environments.

In ES2015 (ES6) or later, if you don't want to be notified about function expressions in an argument list, you can safely disable this rule. Source: http://eslint.org/docs/rules/

  return $.watch([files.src.js, files.test.js], function() {

Close

Suggest using arrow functions as callbacks. (prefer-arrow-callback)

Arrow functions are suited to callbacks, because:

• this keywords in arrow functions bind to the upper scope's.
• The notation of the arrow function is shorter than function expression's.

Rule Details

This rule is aimed to flag usage of function expressions in an argument list.

The following patterns are considered problems:

/*eslint prefer-arrow-callback: "error"*/

foo(function(a) { return a; });
foo(function() { return this.a; }.bind(this));

The following patterns are not considered problems:

/*eslint prefer-arrow-callback: "error"*/
/*eslint-env es6*/

foo(a => a);
foo(function*() { yield; });

// this is not a callback.
var foo = function foo(a) { return a; };

// using `this` without `.bind(this)`.
foo(function() { return this.a; });

// recursively.
foo(function bar(n) { return n && n + bar(n - 1); });

Options

This rule takes one optional argument, an object which is an options object.

allowNamedFunctions

This is a boolean option and it is false by default. When set to true, the rule doesn't warn on named functions used as callbacks.

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

/*eslint prefer-arrow-callback: ["error", { "allowNamedFunctions": true }]*/

foo(function bar() {});

allowUnboundThis

This is a boolean option and it is true by default. When set to false, this option allows the use of this without restriction and checks for dynamically assigned this values such as when using Array.prototype.map with a context argument. Normally, the rule will flag the use of this whenever a function does not use bind() to specify the value of this constantly.

Examples of incorrect code for the { "allowUnboundThis": false } option:

/*eslint prefer-arrow-callback: ["error", { "allowUnboundThis": false }]*/
/*eslint-env es6*/

foo(function() { this.a; });

foo(function() { (() => this); });

someArray.map(function (itm) { return this.doSomething(itm); }, someObject);

When Not To Use It

This rule should not be used in ES3/5 environments.

In ES2015 (ES6) or later, if you don't want to be notified about function expressions in an argument list, you can safely disable this rule. Source: http://eslint.org/docs/rules/