闭包中变量值的改变

来源：互联网发布：人工智能的未来下载编辑：程序博客网时间：2024/05/22 04:48

1.对于闭包中的变量是怎么回事？

function makeCounter() {    var i = 0;    console.log(i);    return function(){        console.log(++i);        console.log(i);    };   }//记住：`counter`和`counter2`都有他们自己的变量 `i`var counter = makeCounter();counter();//1counter();//2makeCounter();var counter2 = makeCounter();counter2();//1counter2();//2

2.异步执行的顺序是怎样的？

for (var i = 0; i < 5; ++i) {  setTimeout(function () {    console.log(i + ' ');  }, 100);}for (var j = 5; j < 10; ++j) {  setTimeout((function (num) {    console.log(num + ' ');  })(j), 100);}for (var k = 10; k < 15; k++) {(function(num){setTimeout(function () {    console.log(num + ' ');  }, 100);})(k);}for (var n = 15; n < 20; n++) {add(n);}function add(num){setTimeout(function(){console.log(num);});

输出的结果是 5,6,7,8，9,15,16,17,18,19,5，5，5，5，5,10,11,12,13,14

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