Map.prototype.size - JavaScript 编辑

The size accessor property returns the number of elements in a Map object.

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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.

Description

The value of size is an integer representing how many entries the Map object has. A set accessor function for size is undefined; you can not change this property.

Examples

Using size

var myMap = new Map();
myMap.set('a', 'alpha');
myMap.set('b', 'beta');
myMap.set('g', 'gamma');

myMap.size // 3

Specifications

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

Browser compatibility

BCD tables only load in the browser

See also

• Map