Use of iterator in ES6

Iterator Concept

Iterator is an interface that provides a unified access mechanism for a variety of data structures. Any data structure can be traversed as long as the iterator interface is deployed (that is, the member that processes the data structure at a time).

Handwriting Iterator interface:

Handwriting Iterator interface
        function iterator (arr) {let
            index=0;
            return{
                next:function () {
                    return index<arr.length?{ Value:arr[index++],done:false}:{value:undefined,done:true}}}
        }
       const arr=[1, ' OK ', 2];
        Const It=iterator (arr);
        Console.log (It.next ());//{value:1, done:false}
        Console.log (It.next ());//{value: "OK", done:false}
        Console.log (It.next ());//{value:2, done:false}
        Console.log (It.next ());//{value:undefined, done:true}
        Console.log (It.next ());//{value:undefined, done:true}

Iterator Interface

The default iterator interface is deployed in the Symbol.iterator property of the data structure, and the Symbol.iterator property itself is also a function, which is the default traversal generator function for the current data structure. Executes this function, it returns a walker.

The data structure of the native iterator interface is as follows:

1) Array

2) Map

3) Set

4) String

5) TypedArray

6) Argument object of the function

For data structures that have a iterator interface deployed, you can use a for loop.

For the Loop
        Const ofarr=[1,2,3];//array for
        (let I of Ofarr) {
            console.log (i)
        }

        //SET data structure
        const Set=new Set ([' A ', ' B ', ' C ']);
        For (let item of Set) {
            Console.log (item);
        }

        Map data Structure
        const map=new Map ([[' A ', 1],[' B ', 2],[' C ', 3]]);
        For (let data of map) {
            console.log (data)
        } for
        (let [key,value] of map) {//struct assignment
            console.log (key, value);
        }

All structures with Symbol.iterator properties have iterator interface
        Const arr=[1,2,3];
        Const set=new Set ([' A ', ' B ', ' C ']);
        Const map=new Map ([[' A ', 1]]);
        Const Itarr=arr[symbol.iterator] ();
        Const Itset=set[symbol.iterator] ();
        Const Itmap=map[symbol.iterator] ();

        Console.log (arr)
        Console.log (Itarr)

        Console.log (set)
        Console.log (itset)

        console.log (map)
        Console.log (Itmap)

        Console.log (Itset.next ());
        Console.log (Itset.next ());
        Console.log (Itset.next ());
        Console.log (Itset.next ());
        Console.log (Itset.next ());