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eb39fafa4f
includes a (minimal) working wrapper Signed-off-by: Dominik Csapak <d.csapak@proxmox.com>
79 lines
1.7 KiB
Markdown
79 lines
1.7 KiB
Markdown
# Suggest using spread syntax instead of `.apply()`. (prefer-spread)
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Before ES2015, one must use `Function.prototype.apply()` to call variadic functions.
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```js
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var args = [1, 2, 3, 4];
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Math.max.apply(Math, args);
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```
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In ES2015, one can use spread syntax to call variadic functions.
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```js
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/*eslint-env es6*/
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var args = [1, 2, 3, 4];
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Math.max(...args);
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```
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## Rule Details
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This rule is aimed to flag usage of `Function.prototype.apply()` in situations where spread syntax could be used instead.
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## Examples
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Examples of **incorrect** code for this rule:
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```js
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/*eslint prefer-spread: "error"*/
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foo.apply(undefined, args);
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foo.apply(null, args);
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obj.foo.apply(obj, args);
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```
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Examples of **correct** code for this rule:
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```js
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/*eslint prefer-spread: "error"*/
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// Using spread syntax
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foo(...args);
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obj.foo(...args);
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// The `this` binding is different.
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foo.apply(obj, args);
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obj.foo.apply(null, args);
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obj.foo.apply(otherObj, args);
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// The argument list is not variadic.
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// Those are warned by the `no-useless-call` rule.
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foo.apply(undefined, [1, 2, 3]);
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foo.apply(null, [1, 2, 3]);
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obj.foo.apply(obj, [1, 2, 3]);
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```
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Known limitations:
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This rule analyzes code statically to check whether or not the `this` argument is changed. So, if the `this` argument is computed in a dynamic expression, this rule cannot detect a violation.
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```js
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/*eslint prefer-spread: "error"*/
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// This warns.
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a[i++].foo.apply(a[i++], args);
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// This does not warn.
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a[++i].foo.apply(a[i], args);
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```
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## When Not To Use It
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This rule should not be used in ES3/5 environments.
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In ES2015 (ES6) or later, if you don't want to be notified about `Function.prototype.apply()` callings, you can safely disable this rule.
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## Related Rules
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* [no-useless-call](no-useless-call.md)
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