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enforce consistent spacing before and after keywords (keyword-spacing)

Keywords are syntax elements of JavaScript, such as function and if. These identifiers have special meaning to the language and so often appear in a different color in code editors. As an important part of the language, style guides often refer to the spacing that should be used around keywords. For example, you might have a style guide that says keywords should be always surrounded by spaces, which would mean if-else statements must look like this:

if (foo) {
    // ...
} else {
    // ...
}

Of course, you could also have a style guide that disallows spaces around keywords.

Rule Details

This rule enforces consistent spacing around keywords and keyword-like tokens: as (in module declarations), async (of async functions), await (of await expressions), break, case, catch, class, const, continue, debugger, default, delete, do, else, export, extends, finally, for, from (in module declarations), function, get (of getters), if, import, in, instanceof, let, new, of (in for-of statements), return, set (of setters), static, super, switch, this, throw, try, typeof, var, void, while, with, and yield. This rule is designed carefully not to conflict with other spacing rules: it does not apply to spacing where other rules report problems.

Options

This rule has an object option:

  • "before": true (default) requires at least one space before keywords
  • "before": false disallows spaces before keywords
  • "after": true (default) requires at least one space after keywords
  • "after": false disallows spaces after keywords
  • "overrides" allows overriding spacing style for specified keywords

before

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

/*eslint keyword-spacing: ["error", { "before": true }]*/

if (foo) {
    //...
}else if (bar) {
    //...
}else {
    //...
}

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

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

if (foo) {
    //...
} else if (bar) {
    //...
} else {
    //...
}

// Avoid conflict with `array-bracket-spacing`
let a = [this];
let b = [function() {}];

// Avoid conflict with `arrow-spacing`
let a = ()=> this.foo;

// Avoid conflict with `block-spacing`
{function foo() {}}

// Avoid conflict with `comma-spacing`
let a = [100,this.foo, this.bar];

// Avoid conflict with `computed-property-spacing`
obj[this.foo] = 0;

// Avoid conflict with `generator-star-spacing`
function *foo() {}

// Avoid conflict with `key-spacing`
let obj = {
    foo:function() {}
};

// Avoid conflict with `object-curly-spacing`
let obj = {foo: this};

// Avoid conflict with `semi-spacing`
let a = this;function foo() {}

// Avoid conflict with `space-in-parens`
(function () {})();

// Avoid conflict with `space-infix-ops`
if ("foo"in {foo: 0}) {}
if (10+this.foo<= this.bar) {}

// Avoid conflict with `jsx-curly-spacing`
let a = <A foo={this.foo} bar={function(){}} />

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

/*eslint keyword-spacing: ["error", { "before": false }]*/

if (foo) {
    //...
} else if (bar) {
    //...
} else {
    //...
}

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

/*eslint keyword-spacing: ["error", { "before": false }]*/

if (foo) {
    //...
}else if (bar) {
    //...
}else {
    //...
}

after

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

/*eslint keyword-spacing: ["error", { "after": true }]*/

if(foo) {
    //...
} else if(bar) {
    //...
} else{
    //...
}

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

/*eslint keyword-spacing: ["error", { "after": true }]*/

if (foo) {
    //...
} else if (bar) {
    //...
} else {
    //...
}

// Avoid conflict with `array-bracket-spacing`
let a = [this];

// Avoid conflict with `arrow-spacing`
let a = ()=> this.foo;

// Avoid conflict with `comma-spacing`
let a = [100, this.foo, this.bar];

// Avoid conflict with `computed-property-spacing`
obj[this.foo] = 0;

// Avoid conflict with `generator-star-spacing`
function* foo() {}

// Avoid conflict with `key-spacing`
let obj = {
    foo:function() {}
};

// Avoid conflict with `func-call-spacing`
class A {
    constructor() {
        super();
    }
}

// Avoid conflict with `object-curly-spacing`
let obj = {foo: this};

// Avoid conflict with `semi-spacing`
let a = this;function foo() {}

// Avoid conflict with `space-before-function-paren`
function() {}

// Avoid conflict with `space-infix-ops`
if ("foo"in{foo: 0}) {}
if (10+this.foo<= this.bar) {}

// Avoid conflict with `space-unary-ops`
function* foo(a) {
    return yield+a;
}

// Avoid conflict with `yield-star-spacing`
function* foo(a) {
    return yield* a;
}

// Avoid conflict with `jsx-curly-spacing`
let a = <A foo={this.foo} bar={function(){}} />

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

/*eslint keyword-spacing: ["error", { "after": false }]*/

if (foo) {
    //...
} else if (bar) {
    //...
} else {
    //...
}

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

/*eslint keyword-spacing: ["error", { "after": false }]*/

if(foo) {
    //...
} else if(bar) {
    //...
} else{
    //...
}

overrides

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

/*eslint keyword-spacing: ["error", { "overrides": {
  "if": { "after": false },
  "for": { "after": false },
  "while": { "after": false }
} }]*/

if(foo) {
    //...
} else if(bar) {
    //...
} else {
    //...
}

for(;;);

while(true) {
  //...
}

When Not To Use It

If you don't want to enforce consistency on keyword spacing, then it's safe to disable this rule.