一. for in 循环
1. 遍历对象
var person={fname:'John', sname:'Doe', age:25}for (var x in person){console.log(x + '==' + person[x])}----------fname==Johnsname==Doeage==25
2. 遍历数组
写法一:
for (var index = 0; index < myArray.length; index++) {console.log(myArray[index]);}`
写法二:
for(var index in arr){console.log(arr[index])}
注:遍历数组时,有以下三点需要注意
点1:
var arr=[1,2,3,4]for(var index in arr){console.log(arr[index]+2)}----------3456
点2:
var arr=['name','age','gender']for(var index in arr){console.log(arr[index]+2)}----------name2age2gender2
点3:
var arr=[1,2,3,4]for(var index in arr){console.log(index+2)}----------021222
有人说:在某些情况下,上面代码将会以任意顺序去遍历数组元素,即显示顺序并不是按我们所想的那样。(有待验证)
因此,for-in 设计的目的是用于遍历包含键值对的对象,对数组并不是那么友好。
遍历数组的话还是用es6的for of循环遍历比较好,改天介绍一下。(有待了解)
二. for each
myArray.forEach(function (value) {console.log(value);});
三. jQuery.each
//遍历数组var arr = ["one", "two", "three", "four", "five"]; var text = "Array "; jQuery.each(arr, function(i, val) { text = text + " #Index:" + i + ":" + val; }); console.log(text); ----------Array #Index:0:one #Index:1:two #Index:2:three #Index:3:four #Index:4:five //遍历对象var obj = { one: 1, two: 2, three: 3, four: 4, five: 5 }; text = "Object "; jQuery.each(obj, function(i, val) { text = text + "Key:" + i + ", Value:" + val; }); console.log(text); ----------Object Key:one, Value:1Key:two, Value:2Key:three, Value:3Key:four, Value:4Key:five, Value:5
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