---
title: consistent-this - Rules
layout: doc
edit_link: https://github.com/eslint/eslint/edit/master/docs/rules/consistent-this.md
---
<!-- Note: No pull requests accepted for this file. See README.md in the root directory for details. -->

# Require Consistent This (consistent-this)

It is often necessary to capture the current execution context in order to make it available subsequently. A prominent example of this are jQuery callbacks:

```js
var that = this;
jQuery('li').click(function (event) {
    // here, "this" is the HTMLElement where the click event occurred
    that.setFoo(42);
});
```

There are many commonly used aliases for `this` such as `that`, `self` or `me`. It is desirable to ensure that whichever alias the team agrees upon is used consistently throughout the application.

## Rule Details

This rule enforces two things about variables with the designated alias names for `this`:

* If a variable with a designated name is declared, it *must* be either initialized (in the declaration) or assigned (in the same scope as the declaration) the value `this`.
* If a variable is initialized or assigned the value `this`, the name of the variable *must* be a designated alias.

## Options

This rule has one or more string options:

* designated alias names for `this` (default `"that"`)

Examples of **incorrect** code for this rule with the default `"that"` option:

```js
/*eslint consistent-this: ["error", "that"]*/

var that = 42;

var self = this;

that = 42;

self = this;
```

Examples of **correct** code for this rule with the default `"that"` option:

```js
/*eslint consistent-this: ["error", "that"]*/

var that = this;

var self = 42;

var self;

that = this;

foo.bar = this;
```

Examples of **incorrect** code for this rule with the default `"that"` option, if the variable is not initialized:

```js
/*eslint consistent-this: ["error", "that"]*/

var that;
function f() {
    that = this;
}
```

Examples of **correct** code for this rule with the default `"that"` option, if the variable is not initialized:

```js
/*eslint consistent-this: ["error", "that"]*/

var that;
that = this;

var foo, that;
foo = 42;
that = this;
```

## When Not To Use It

If you need to capture nested context, `consistent-this` is going to be problematic. Code of that nature is usually difficult to read and maintain and you should consider refactoring it.

## Version

This rule was introduced in ESLint 0.0.9.

## Resources

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