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]+"\n";
 }
}
alert(msg);