$.each 和$(selector).each()的区别
$.each()
译自官方手册:jQuery.each()
对数组或对对象内容进行循环处理
jQuery.each( collection, callback(indexInArray, valueOfElement) )
collection 遍历的对象或数组
callback(indexInArray, valueOfElement) 在每一个对象上调用的函数
说明
一个通用的遍历函数 , 可以用来遍历对象和数组. 数组和含有一个length属性的伪数组对象 (伪数组对象如function的arguments对象)以数字索引进行遍历,从0到length-1, 其它的对象通过的属性进行遍历.
$.each()与$(selector).each()不同, 后者专用于jquery对象的遍历, 前者可用于遍历任何的集合(无论是数组或对象),如果是数组,回调函数每次传入数组的索引和对应的值(值亦可以通过this 关键字获取,但javascript总会包装this 值作为一个对象—尽管是一个字符串或是一个数字),方法会返回被遍历对象的第一参数
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
//例子:———传入数组
<!DOCTYPE html> <html> <head> <script src=”http://code.jquery.com/jquery-latest.js”></script> </head> <body> <script> $.each([52, 97], function(index, value) { alert(index + ‘: ‘ + value); }); </script> </body> </html>
//输出
0: 52
1: 97
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
//例子:———如果一个映射作为集合使用,回调函数每次传入一个键-值对
<!DOCTYPE html> <html> <head> <script src=”http://code.jquery.com/jquery-latest.js”></script> </head> <body> <script> var map = { ‘flammable’: ‘inflammable’, ‘duh’: ‘no duh’ }; $.each(map, function(key, value) { alert(key + ‘: ‘ + value); }); </script> </body> </html>
//输出
flammable: inflammable
duh: no duh
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
//例子:———回调函数中 return false时可以退出$.each(), 如果返回一个非false 即会像在for循环中使用continue 一样, 会立即进入下一个遍历
<!DOCTYPE html> <html> <head> <style> div { color:blue; } div#five { color:red; } </style> <script src=”http://code.jquery.com/jquery-latest.js”></script> </head> <body> <div id=”one”></div> <div id=”two”></div> <div id=”three”></div> <div id=”four”></div> <div id=”five”></div> <script> var arr = [ "one", "two", "three", "four", "five" ];//数组 var obj = { one:1, two:2, three:3, four:4, five:5 }; // 对象 jQuery.each(arr, function() { // this 指定值 $(“#” + this).text(“Mine is ” + this + “.”); // this指向为数组的值, 如one, two return (this != “three”); // 如果this = three 则退出遍历 }); jQuery.each(obj, function(i, val) { // i 指向键, val指定值 $(“#” + i).append(document.createTextNode(” – ” + val)); }); </script> </body> </html>
// 输出
//例子:———遍历数组的项, 传入index和value
<!DOCTYPE html> <html> <head> <script src=”http://code.jquery.com/jquery-latest.js”></script> </head> <body> <script> $.each( ['a','b','c'], function(i, l){ alert( “Index #” + i + “: ” + l ); }); </script> </body> </html>
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
//例子:———遍历对象的属性,传入 key和value
<!DOCTYPE html> <html> <head> <script src=”http://code.jquery.com/jquery-latest.js”></script> </head> <body> <script> $.each( { name: “John”, lang: “JS” }, function(k, v){ alert( “Key: ” + k + “, Value: ” + v ); }); </script> </body> </html>
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
1. 如果不想输出第一项 (使用retrun true)进入 下一遍历
<!DOCTYPE html> <html> <head> <script src=”http://code.jquery.com/jquery-latest.js”></script> </head> <body> <script> var myArray=["skipThis", "dothis", "andThis"]; $.each(myArray, function(index, value) { if (index == 0) { return true; // equivalent to ‘continue’ with a normal for loop } // else do stuff… alert (index + “: “+ value); }); </script> </body> </html>
