譯自官方手冊:jQuery.each()
對數組或對對象內容進行循環處理
jQuery.each( collection, callback(indexInArray, valueOfElement) )
collection 遍歷的對象或數組
callback(indexInArray, valueOfElement) 在每一個對象上調用的函數
說明
一個通用的遍歷函數 , 可以用來遍歷對象和數組. 數組和含有一個length屬性的僞數組對象 (僞數組對象如function的arguments對象)以數字索引進行遍歷,從0到length-1, 其它的對象通過的屬性進行遍歷.
$.each()與$(selector).each()不同, 後者專用於jquery對象的遍歷, 前者可用於遍歷任何的集合(無論是數組或對象),如果是數組,回調函數每次傳入數組的索引和對應的值(值亦可以通過this 關鍵字獲取,但javascript總會包裝this 值作爲一個對象—儘管是一個字符串或是一個數字),方法會返回被遍歷對象的第一參數
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
//例子:———傳入數組
<!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>
//輸出
0: 52
1: 97
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
//例子:———如果一個映射作爲集合使用,回調函數每次傳入一個鍵-值對
<!DOCTYPE html>
<html>
<head>
<script src=”http://code.jquery.com/jquery-latest.js”></script>
</head>
<body>
<script>
var map = {
‘flammable’: ‘inflammable’,
‘duh’: ‘no duh’
};
$.each(map, function(key, value) {
alert(key + ‘: ‘ + value);
});
</script>
</body>
</html>
//輸出
flammable: inflammable
duh: no duh
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
//例子:———回調函數中 return false時可以退出$.each(), 如果返回一個非false 即會像在for循環中使用continue 一樣, 會立即進入下一個遍歷
<!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" ];//數組
var obj = { one:1, two:2, three:3, four:4, five:5 }; // 對象
jQuery.each(arr, function() { // this 指定值
$(“#” + this).text(“Mine is ” + this + “.”); // this指向爲數組的值, 如one, two
return (this != “three”); // 如果this = three 則退出遍歷
});
jQuery.each(obj, function(i, val) { // i 指向鍵, val指定值
$(“#” + i).append(document.createTextNode(” – ” + val));
});
</script>
</body>
</html>
// 輸出
//例子:———遍歷數組的項, 傳入index和value
<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:———遍歷對象的屬性,傳入 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>
正自評論的例子:
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
1. 如果不想輸出第一項 (使用retrun true)進入 下一遍歷
<!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>