Set.prototype.has() - JavaScript 编辑

The has() method returns a boolean indicating whether an element with the specified value exists in a Set object or not.

The source for this interactive example is stored in a GitHub repository. If you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request.

The source for this interactive example is stored in a GitHub repository. If you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request.

Syntax

mySet.has(value);

Parameters

value

The value to test for presence in the Set object.

Return value

Returns true if an element with the specified value exists in the Set object; otherwise false.

Note: Technically speaking, has() uses the Same-value-zero algorithm to determine whether the given element is found.

Examples

Using the has() method

var mySet = new Set();
mySet.add('foo');

mySet.has('foo');  // returns true
mySet.has('bar');  // returns false

var set1 = new Set();
var obj1 = {'key1': 1};
set1.add(obj1);

set1.has(obj1);        // returns true
set1.has({'key1': 1}); // returns false because they are different object references
set1.add({'key1': 1}); // now set1 contains 2 entries

Specifications

Specification
ECMAScript (ECMA-262) The definition of 'Set.prototype.has' in that specification.

Browser compatibility

BCD tables only load in the browser

See also

• Set
• Set.prototype.add()
• Set.prototype.delete()