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);