#prefer-spread

#Configuration

import { defineConfig, js } from '@rslint/core';

export default defineConfig([
  js.configs.recommended,
  {
    rules: {
      'prefer-spread': 'error',
    },
  },
]);

#Rule Details

Suggest using the spread operator instead of .apply().

Before ES2015, Function.prototype.apply() was the only way to call a variadic function with an array of arguments. With the spread operator (...), function(...args) achieves the same effect more concisely and also works in new expressions, which .apply() does not support.

This rule flags .apply() calls that are interchangeable with a spread call:

• The second argument of .apply() is neither an array literal nor a spread element (those forms already behave like a spread call).
• The first argument preserves the this binding of the applied function:
  • When the function is not a member expression, only null / undefined / void 0 pass (otherwise the this binding may change on migration).
  • When the function is a member expression (e.g. obj.foo.apply(obj, args)), the first argument must produce the same token stream as the member's object (e.g. obj on both sides).

Examples of incorrect code for this rule:

foo.apply(undefined, args);
foo.apply(null, args);
obj.foo.apply(obj, args);

Examples of correct code for this rule:

// The `this` binding is changed deliberately
foo.apply(obj, args);
obj.foo.apply(null, args);
obj.foo.apply(otherObj, args);

// The second argument is not variadic
foo.apply(undefined, [1, 2, 3]);
obj.foo.apply(obj, [1, 2, 3]);

// Already using a spread call
obj.foo(...args);

#Original Documentation

• ESLint prefer-spread