JS: Map.prototype

By Xah Lee. Date: . Last updated: .

New in ES2015.

Map.prototype is the value of the property key "prototype" of the Map object.

〔►see JS: Map Object

console.log( Map.hasOwnProperty ( "prototype" ) ); // true

Type of Map.prototype is object.

〔►see JS: Data Types

// type of Map.prototype
console.log ( typeof Map.prototype === "object" ); // true
console.log ( Object.prototype.toString.call( Map.prototype ) === "[object Map]" ) // true

Parent of Map.prototype is Object.prototype.

// parent of Map.prototype
console.log ( Object.getPrototypeOf ( Map.prototype ) === Object.prototype ); // true

〔►see JS: Prototype and Inheritance

Map.prototype is the parent of all map instances.

console.log ( Object.getPrototypeOf ( new Map() ) === Map.prototype ); // true

The purpose of Map.prototype object is to provides methods and properties useful for all map instances.

Properties

  1. Map.prototype.constructor
  2. get Map.prototype.size

get, set

  1. Map.prototype.get ( key )
  2. Map.prototype.set ( key , value )
  3. Map.prototype.has ( key )
  4. Map.prototype.delete ( key )
  5. Map.prototype.clear ( )

loop

  1. Map.prototype.forEach ( f, this )
  2. Map.prototype.keys ( )
  3. Map.prototype.values ( )
  4. Map.prototype.entries ( )

misc

  1. Map.prototype [ Symbol.iterator ]( )
  2. Map.prototype [ Symbol.toStringTag ]

Map.prototype.constructor

Map.prototype.constructor → value is Map

console.log ( Map.prototype.constructor === Map ); // true
console.log ( (new Map()).constructor === Map ); // true

〔►see JS: Map Object

〔►see JS: Property Key "constructor"

ECMAScript 2015 §Keyed Collection#sec-map.prototype.constructor

Map.prototype.size

map_obj.size → returns the total count of entries in map_obj.

size is a getter property. 〔►see JS: Getter/Mapter Properties

// size of map
var m = new Map([[3, "n3"], [4, "n4"], [5, "n5"] ]);
console.log(m.size) // 3

〔►see JS: Getter/Setter Properties

ECMAScript 2015 §Keyed Collection#sec-get-map.prototype.size

Map.prototype.get

〔►see JS: Map.prototype.get

Map.prototype.set

〔►see JS: Map.prototype.set

Map.prototype.has

〔►see JS: Map.prototype.has

Map.prototype.delete

〔►see JS: Map.prototype.delete

Map.prototype.clear

〔►see JS: Map.prototype.clear

Map.prototype.forEach

〔►see JS: Map.prototype.forEach

Map.prototype.keys

〔►see JS: Map.prototype.keys

Map.prototype.values

〔►see JS: Map.prototype.values

Map.prototype.entries

〔►see JS: Map.prototype.entries

Map.prototype [ Symbol.iterator ]

Map.prototype [ Symbol.iterator ] ( ) → same as Map.prototype.entries ( )

〔►see JS: Map.prototype.entries

ECMAScript 2015 §Keyed Collection#sec-map.prototype-@@iterator

Map.prototype [ Symbol.toStringTag ]

Map.prototype [ Symbol.toStringTag ] → Value is the string "Map".

〔►see JS: Determine Type of Object

console.log ( Map.prototype [ Symbol.toStringTag ] === "Map" ); // true

ECMAScript 2015 §Keyed Collection#sec-map.prototype-@@tostringtag

Reference

ECMAScript 2015 §Keyed Collection#sec-properties-of-the-map-prototype-object

Map Topic

  1. JS: the Map Object Tutorial
  2. JS: Map Object
  3. JS: Map.prototype
  4. JS: Iterate Over Map Object
  5. JS: Convert Object to/from Map
Like what you read? Buy JavaScript in Depth