JQuery中的each函数札记1 _Web前端

JQuery中的each函数笔记1

 //函数原型
 jQuery.each( collection, callback(indexInArray, valueOfElement) )
 //collection The object or array to iterate over.
 //collection 需要迭代输出的对象
 
 //callback(indexInArray, valueOfElement) The function that will be executed on every object.
 //callback(indexInArray, valueOfElement) 回调函数，这个函数会对每一个对象执行
    //-- indexInArray 对象索引号/对象属性号
    //-- valueOfElement  对象的值

 //Summary 
A generic iterator function, which can be used to seamlessly iterate over both objects and arrays. Arrays and array-like objects with a length property (such as a function's arguments object) are iterated by numeric index, from 0 to length-1. Other objects are iterated via their named properties.
/*
这是一个通用的迭代函数，它可以无缝的迭代输出对象和数组，数组和有一个长度属性数组对象(就像函数中的 参数对象 )可以用它们相应的索引值，从0到length-1 迭代输出,其他的对象(如map对象)可以通过他们的名称属性进行迭代。
*/

//官方秘籍第一句就说了
The $.each() function is not the same as $(selector).each()....
//此 $.each() 非 $(selector).each(), 两者压根不是一回事儿。
//$(selector).each() 参考这里 http://api.jquery.com/each/

//数组
$.each([52, 97], function(index, value) { 
  alert(index + ': ' + value); 
});
//output result:
//0: 52
//1: 97

//Map
var map = { 
  'flammable': 'inflammable', 
  'duh': 'no duh' 
}; 
$.each(map, function(key, value) { 
  alert(key + ': ' + value); 
});
//output result:
//flammable: inflammable
//duh: no duh

We can break the $.each() loop at a particular iteration by making the callback function return false. Returning non-false is the same as a continue statement in a for loop; it will skip immediately to the next iteration.
/*
我们可以跳出$.each()的循环， return false 结束循环，continue 跳过此次循环
*/

<!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" ];
    var obj = { one:1, two:2, three:3, four:4, five:5 };

    jQuery.each(arr, function() {
      $("#" + this).text("Mine is " + this + ".");
       return (this != "three"); // will stop running after "three"
   });

    jQuery.each(obj, function(i, val) {
      $("#" + i).append(document.createTextNode(" - " + val));
    });
</script>

</body>
</html>

结果
Mine is one. - 1
Mine is two. - 2
Mine is three. - 3
- 4
- 5

//另外两个
Example: Iterates over items in an array, accessing both the current item and its index.
$.each( ['a','b','c'], function(i, l){
   alert( "Index #" + i + ": " + l );
 });

Example: Iterates over the properties in an object, accessing both the current item and its key.
$.each( { name: "John", lang: "JS" }, function(k, v){
   alert( "Key: " + k + ", Value: " + v );
 });

JQuery中的each函数 札记1

JQuery中的each函数札记1