Map.prototype.has() - JavaScript 编辑

The has() method returns a boolean indicating whether an element with the specified key exists or not.

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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

myMap.has(key)

Parameters

key

The key of the element to test for presence in the Map object.

Return value

true if an element with the specified key exists in the Map object; otherwise false.

Examples

Using has()

let myMap = new Map()
myMap.set('bar', "foo")

myMap.has('bar')   // returns true
myMap.has('baz')   // returns false

Specifications

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

Browser compatibility

BCD tables only load in the browser

See also

• Map
• Map.prototype.set()
• Map.prototype.get()