JS Map and set

Map

MapIs the structure of a set of key-value pairs with extremely fast lookup speeds.

var m = new Map([[‘Michael‘, 95], [‘Bob‘, 75], [‘Tracy‘, 85]]);m.get(‘Michael‘); // 95

Set

Setand Map similar, is also a set of keys, but does not store value. Since key cannot be duplicated, therefore, Set there is no duplicate key in the.

To create one Set , you need to provide one Array as input, or create a null directly Set :

var s1 = new Set(); // 空Setvar s2 = new Set([1, 2, 3]); // 含1, 2, 3

Traversal Array can take the subscript loop, traverse Map and Set cannot use subscript. In order to unify collection types, the ES6 standard introduces new iterable types Array , Map and Set all of them belong to iterable types.

A iterable collection with a type can traverse through a new for ... of loop.

for ... ofThe loop is the new syntax introduced by ES6

JS Map and set