generator生成器iterator遍历器和yield

阅读目录

• generator方法()返回一个iterator
• 使用generator时永远先去调用generator()方法
• for of对iterator的调用过程(babel参照)
• yield* 后跟generator(生成器嵌套)

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generator方法()返回一个iterator

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使用generator时永远先去调用generator()方法

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for of对iterator的调用过程(babel参照)

1,_iterator.next() 每次循环 调用iterator的next()
2,var v = _step.value;将next().value赋值给当前项
babel地址

var arr=[1,2];
for(let v of arr){
  console.log(v)
}

"use strict";

var arr = [1, 2];
var _iteratorNormalCompletion = true;
var _didIteratorError = false;
var _iteratorError = undefined;

try {
  for (var _iterator = arr[Symbol.iterator](), _step; !(_iteratorNormalCompletion = (_step = _iterator.next()).done); _iteratorNormalCompletion = true) {
    var v = _step.value;

    console.log(v);
  }
} catch (err) {
  _didIteratorError = true;
  _iteratorError = err;
} finally {
  try {
    if (!_iteratorNormalCompletion && _iterator.return) {
      _iterator.return();
    }
  } finally {
    if (_didIteratorError) {
      throw _iteratorError;
    }
  }
}

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yield* 后跟generator(生成器嵌套)

function * g1(){
	yield 'a'
	yield 'b'
}
function * g2(){
	yield 1
	yield* g1()
	yield 2
}
for(let v of g2()){
	console.log(v)
}