JavaScript中循环遍历Array与Map的方法小结

js循环数组各种方法 eg1：


for (var i = 0; i < myStringArray.length; i++) {
alert(myStringArray[i]);
//Do something
}


eg2：


Array.prototype.foo = "foo!";
var array = ['a', 'b', 'c'];

for (var i in array) {
alert(array[i]);
}

for(var i in this.$GLOBAL_DETAIL.album_photo_ids){if(this.$GLOBAL_DETAIL.album_photo_ids[i] == "3487675024077108") alert(this.$GLOBAL_DETAIL.album_photo_ids[i]);}


eg3：


[1,2,3,4].map( function(item) {
alert(item);
})


eg4：


var x = [1,2,3,4].map( function(item) { return item * 10; } );

// And now x is [10,20,30,40]


eg5：


var myStringArray = [ "Hello", "World" ]
var len = myStringArray.length
for (var i=0; i<len; ++i) {
if (i in myStringArray) {
var s = myStringArray[i];
... do something with s ...
}
}


eg6：


var myStringArray = [ "Hello", "World" ]
myStringArray.forEach( function(s) {
... do something with s ...
} )


eg7：


var i=0,item,items = ['one','two','three'];
while(item=items[i++]){
console.log(item);
}

// logs: 'one','two','three'

and for the reverse order, an even more efficient loop
var items = ['one','two','three'], i=items.length;
while(i--){
console.log(items[i]);
}

// logs: 'three','two','one'

or the classical for loop
var items = ['one','two','three']
for(var i=0,l=items.length; i < l ; i++){
console.log(items[i]);
}

// logs: 'one','two','three'


eg8：


var myStringArray = ['Hello', 'World']; // array uses [] not {}
for (var i in myStringArray) {
console.log(i + ' -> ' + myStringArray[i]); // i is the index/key, not the item
}


js循环map，获取所有的key和value eg1：


//Page地址
pageUrl : {
menu : "loadPage.htm?url=/collect/menu.page", // 进入菜单页面
guangfaPage : "loadPage.htm?url=/collect/menu.page", // 进入广发信息收集页面
pinganPage : "loadPage.htm?url=/collect/menu.page", // 进入平安信息收集页面
nuonuoPage : "loadPage.htm?url=/collect/menu.page", // 进入诺诺信息收集页面
youbangPage : "loadPage.htm?url=/collect/menu.page", // 进入友邦信息收集页面
inputMobileNo : "loadPage.htm?url=/collect/inputMobileNo.page", // 进入输入手机号页面
readIdCard : "loadPage.htm?url=/collect/readIdCard.page", // 进入读取身份证页面
member : "loadPage.htm?url=/collect/member.page", // 进入输入会员卡号页面
bankCard : "loadPage.htm?url=/collect/bankCard.page", // 进入插入银行卡页面
url : "loadPage.htm?url=/collect/url.page" // 进入跳转url页面
},

for(var key in this.pageUrl){
alert(key+" : "+this.pageUrl[key]);
}


eg2：


var obj = {
"a": 1,
"b": 2,
"c": 3
};

for (var prop in obj) {
if (obj.hasOwnProperty(prop)) {
// or if (Object.prototype.hasOwnProperty.call(obj,prop)) for safety...
alert("prop: " + prop + " value: " + obj[prop])
}
}


双重Map循环 eg：


var msg = "";
for(var key in Pin) {
for(var i in Pin[key]){
msg+=i+": "+Pin[key][i]+"
";
}
}
alert(msg);




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