function
expressions (func-names)A pattern that's becoming more common is to give function expressions names to aid in debugging. For example:
Foo.prototype.bar = function bar() {};
Adding the second bar
in the above example is optional. If you leave off the function name then when the function throws an exception you are likely to get something similar to anonymous function
in the stack trace. If you provide the optional name for a function expression then you will get the name of the function expression in the stack trace.
This rule can enforce or disallow the use of named function expressions.
This rule has a string option:
"always"
(default) requires function expressions to have a name"as-needed"
requires function expressions to have a name, if the name cannot be assigned automatically in an ES6 environment"never"
disallows named function expressions, except in recursive functions, where a name is neededThis rule has an object option:
"generators": "always" | "as-needed" | "never"
"always"
require named generators"as-needed"
require named generators if the name cannot be assigned automatically in an ES6 environment."never"
disallow named generators where possible.When a value for generators
is not provided the behavior for generator functions falls back to the base option.
Examples of incorrect code for this rule with the default "always"
option:
/*eslint func-names: ["error", "always"]*/
Foo.prototype.bar = function() {};
const cat = {
meow: function() {}
}
(function() {
// ...
}())
Examples of correct code for this rule with the default "always"
option:
/*eslint func-names: ["error", "always"]*/
Foo.prototype.bar = function bar() {};
const cat = {
meow() {}
}
(function bar() {
// ...
}())
ECMAScript 6 introduced a name
property on all functions. The value of name
is determined by evaluating the code around the function to see if a name can be inferred. For example, a function assigned to a variable will automatically have a name
property equal to the name of the variable. The value of name
is then used in stack traces for easier debugging.
Examples of incorrect code for this rule with the "as-needed"
option:
/*eslint func-names: ["error", "as-needed"]*/
Foo.prototype.bar = function() {};
(function() {
// ...
}())
Examples of correct code for this rule with the "as-needed"
option:
/*eslint func-names: ["error", "as-needed"]*/
var bar = function() {};
const cat = {
meow: function() {}
}
(function bar() {
// ...
}())
Examples of incorrect code for this rule with the "never"
option:
/*eslint func-names: ["error", "never"]*/
Foo.prototype.bar = function bar() {};
(function bar() {
// ...
}())
Examples of correct code for this rule with the "never"
option:
/*eslint func-names: ["error", "never"]*/
Foo.prototype.bar = function() {};
(function() {
// ...
}())
Examples of incorrect code for this rule with the "always", { "generators": "as-needed" }
options:
/*eslint func-names: ["error", "always", { "generators": "as-needed" }]*/
(function*() {
// ...
}())
Examples of correct code for this rule with the "always", { "generators": "as-needed" }
options:
/*eslint func-names: ["error", "always", { "generators": "as-needed" }]*/
var foo = function*() {};
Examples of incorrect code for this rule with the "always", { "generators": "never" }
options:
/*eslint func-names: ["error", "always", { "generators": "never" }]*/
var foo = bar(function *baz() {});
Examples of correct code for this rule with the "always", { "generators": "never" }
options:
/*eslint func-names: ["error", "always", { "generators": "never" }]*/
var foo = bar(function *() {});
Examples of incorrect code for this rule with the "as-needed", { "generators": "never" }
options:
/*eslint func-names: ["error", "as-needed", { "generators": "never" }]*/
var foo = bar(function *baz() {});
Examples of correct code for this rule with the "as-needed", { "generators": "never" }
options:
/*eslint func-names: ["error", "as-needed", { "generators": "never" }]*/
var foo = bar(function *() {});
Examples of incorrect code for this rule with the "never", { "generators": "always" }
options:
/*eslint func-names: ["error", "never", { "generators": "always" }]*/
var foo = bar(function *() {});
Examples of correct code for this rule with the "never", { "generators": "always" }
options:
/*eslint func-names: ["error", "never", { "generators": "always" }]*/
var foo = bar(function *baz() {});
This rule was introduced in ESLint 0.4.0.
© JS Foundation and other contributors
Licensed under the MIT License.
https://eslint.org/docs/rules/func-names