---
title: rest-spread-spacing - Rules
layout: doc
---
<!-- Note: No pull requests accepted for this file. See README.md in the root directory for details. -->

# Enforce spacing between rest and spread operators and their expressions (rest-spread-spacing)

(fixable) The `--fix` option on the [command line](../user-guide/command-line-interface#fix) can automatically fix some of the problems reported by this rule.

ES2015 introduced the rest and spread operators, which expand an iterable structure into its individual parts. Some examples of their usage are as follows:

```js
let numArr = [1, 2, 3];
function add(a, b, c) {
    return a + b + c;
}
add(...numArr); // -> 6

let arr1 = [1, 2, 3];
let arr2 = [4, 5, 6];
arr1.push(...arr2); // -> [1, 2, 3, 4, 5, 6]

let [a, b, ...arr] = [1, 2, 3, 4, 5];
a; // -> 1
b // -> 2
arr; // ->  [3, 4, 5]

function numArgs(...args) {
  return args.length;
}
numArgs(a, b, c); // -> 3
```

In addition to the above, there is currently a proposal to add object rest and spread properties to the spec. They can be used as follows:

```js

let { x, y, ...z } = { x: 1, y: 2, a: 3, b: 4 };
x; // -> 1
y; // -> 2
z; // -> { a: 3, b: 4 }

let n = { x, y, ...z };
n; // -> { x: 1, y: 2, a: 3, b: 4 }
```

As with other operators, whitespace is allowed between the rest or spread operator and the expression it is operating on, which can lead to inconsistent spacing within a codebase.

## Rule Details

This rule aims to enforce consistent spacing between rest and spread operators and their expressions. The rule also supports the currently experimental object rest and spread properties when enabled:

```json
{
    "parserOptions": {
        "ecmaVersion": 6,
        "ecmaFeatures": {
            "experimentalObjectRestSpread": true
        }
    }
}
```

Please read the user guide's section on [configuring parser options](https://eslint.org/docs/user-guide/configuring#specifying-parser-options) to learn more.

## Options

This rule takes one option: a string with the value of `"never"` or `"always"`. The default value is `"never"`.

### "never"

When using the default `"never"` option, whitespace is not allowed between spread operators and their expressions.

```json
rest-spread-spacing: ["error"]
```

or

```json
rest-spread-spacing: ["error", "never"]
```

Examples of **incorrect** code for this rule with `"never"`:

```js
/*eslint rest-spread-spacing: ["error", "never"]*/

fn(... args)
[... arr, 4, 5, 6]
let [a, b, ... arr] = [1, 2, 3, 4, 5];
function fn(... args) { console.log(args); }
let { x, y, ... z } = { x: 1, y: 2, a: 3, b: 4 };
let n = { x, y, ... z };
```

Examples of **correct** code for this rule with `"never"`:

```js
/*eslint rest-spread-spacing: ["error", "never"]*/

fn(...args)
[...arr, 4, 5, 6]
let [a, b, ...arr] = [1, 2, 3, 4, 5];
function fn(...args) { console.log(args); }
let { x, y, ...z } = { x: 1, y: 2, a: 3, b: 4 };
let n = { x, y, ...z };
```

### "always"

When using the `"always"` option, whitespace is required between spread operators and their expressions.

```json
rest-spread-spacing: ["error", "always"]
```

Examples of **incorrect** code for this rule with `"always"`:

```js
/*eslint rest-spread-spacing:["error", "always"]*/

fn(...args)
[...arr, 4, 5, 6]
let [a, b, ...arr] = [1, 2, 3, 4, 5];
function fn(...args) { console.log(args); }
let { x, y, ...z } = { x: 1, y: 2, a: 3, b: 4 };
let n = { x, y, ...z };
```

Examples of **correct** code for this rule with `"always"`:

```js
/*eslint rest-spread-spacing: ["error", "always"]*/

fn(... args)
[... arr, 4, 5, 6]
let [a, b, ... arr] = [1, 2, 3, 4, 5];
function fn(... args) { console.log(args); }
let { x, y, ... z } = { x: 1, y: 2, a: 3, b: 4 };
let n = { x, y, ... z };
```

## When Not To Use It

You can safely disable this rule if you do not care about enforcing consistent spacing between spread operators and their expressions.

## Further Reading

* [Object Rest/Spread Properties for ECMAScript](https://github.com/sebmarkbage/ecmascript-rest-spread)

## Version

This rule was introduced in ESLint 2.12.0.

## Resources

* [Rule source](https://github.com/eslint/eslint/tree/master/lib/rules/rest-spread-spacing.js)
* [Documentation source](https://github.com/eslint/eslint/tree/master/docs/rules/rest-spread-spacing.md)
