Spread operator and iterators in JavaScript
The spread operator expands any
object that has an iterator. This will
take the default iterator. Let's look
at an example. Let we have the following
Map collection:
let map = new Map();
map.set('a', 1);
map.set('b', 2);
map.set('c', 3);
By default, when decomposed, a two-dimensional array will be obtained:
let arr = [...map];
console.log(arr); // [['a', 1], ['b', 2], ['c', 3]]
To obtain an array of keys, we decompose the corresponding iterator:
let arr = [...map.keys()];
console.log(arr); // ['a', 'b', 'c']
Let's do the same to get an array of values:
let arr = [...map.values()];
console.log(arr); // [1, 2, 3]
Expand the next object with spread operator:
let obj = {
a: 1,
b: 2,
c: 3,
[Symbol.iterator]: function *(){
for (let key in this){
yield this[key];
}
}
};
