es6迭代器iterator案例理解

案例一

var obj = {
    
    k1: '111', k2: '2222', k3: '333'};
obj[Symbol.iterator] = function(){
    
    
	let keys = Object.keys(this);
	let len = keys.length;
	let idx = -1;
	return {
    
    
		next: function(){
    
    
			idx++;
			return {
    
    
				value: [idx, keys[idx]],
				done: idx>=len 
			}
		}
	}
}
for (let [key, val] of obj){
    
    
	console.log(key, val);
}

案例二(yield)

ar obj = {
    
    k1: '111', k2: '2222', k3: '333'};
obj[Symbol.iterator] = function*(){
    
    
	for(let item of Object.keys(this)) {
    
    
		yield item;
	}
}
for (let [key, val] of obj){
    
    
	console.log(key, val);
}

Generator 函数里的iterator案例

function* fibs() {
    
    
  let a = 0;
  let b = 1;
  while (true) {
    
    
    yield a;
    [a, b] = [b, a + b];
  }
}

let [first, second, third, fourth, fifth, sixth] = fibs();