for 循环和 for/in 循环的区别

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注意:for/in 循环会访问该对象的原型,应该用在非数组对象的遍历上,不建议使用该方法遍历数组。

示例:

<!DOCTYPE html><html lang="en"><head>    <meta charset="UTF-8">    <title>Title</title></head><body><script>    var myCars = new Array()    myCars[0] = "Saab"    myCars[1] = "Volvo"    myCars[2] = "BMW"    Array.prototype.newObject = 1234;    Array.prototype.newfunction = function () { console.log("new function");}    console.info("数组长度:")    console.log(myCars.length)    console.info("for 循环")    for(var i=0;i<myCars.length;i++){        console.log(myCars[i])    }    console.info("for in 循环")    for (var x in myCars)    {        console.log(myCars[x])    }    console.info("for of 循环(ES6)")    for (var k of myCars)    {        console.log(k)    }</script></body></html>

结果:

0 0