JavaScript: Map.prototype.entries
New in JS2015.
map_obj.entries ( )
-
Return a Iterable (also is a Iterator) for the map instance map_obj.
Each yield is a array of the form
[key, value]
.
const mm = new Map([[1,2],[3,4]]); for (let e of mm.entries()) { console.log( e, Array.isArray ( e ) ); } // prints // [ 1, 2 ] true // [ 3, 4 ] true for (let e of mm) { console.log( e, Array.isArray ( e ) ); } // prints // [ 1, 2 ] true // [ 3, 4 ] true
This example shows the result is iterator and iterable:
let mp = new Map( [[1,2], [3,4]]); console.log( mp.entries ); // [Function: entries] // result is a function that returns a iterator object // call it console.log( mp.entries() ); // MapIterator { [ 1, 2 ], [ 3, 4 ] } // result is a iterator object // is also a iterable console.log( Symbol.iterator in ( mp.entries() ) ); // true
Note: Map.prototype.entries
is the same as Map.prototype[Symbol.iterator]
[see Symbol Tutorial]
ECMAScript 2015 §Keyed Collection#sec-map.prototype-@@iterator