js array operations pop, push, unshift, splice, shift_javascript skills

Copy code The code is as follows:

<script> <BR>Array.prototype.pop=function( ){ <BR> if(this.length!=0)this.length--; <BR> return this; <BR> } <BR></script>

pop method
Removes the last element from an array and returns that element.

arrayObj.pop( )

The required arrayObj reference is an Array object.

Explanation
If the array is empty, undefined will be returned.

Copy code The code is as follows:

var a=[1,2,3,4]
a.pop()
alert(a)
alert(a.pop())<script> <BR></script>

push method
Adds a new element to an array and returns the new length of the array.

arrayObj.push([item1 [item2 [. . . [itemN ]]]])

Parameters
arrayObj

Required. An Array object.

item, item2,. . . itemN

Optional. The new element of this Array.

Description The
push method will add new elements in the order in which they appear. If one of the arguments is an array, the array is added to the array as a single element. If you want to combine elements from two or more arrays, use the concat method.

Copy code The code is as follows:

Array.prototype.push=function(){ 
var len=arguments.length;
if(len>0)for(var i=0;i return this.length;
}
var a=[1,2,3,4]
a.push(5)
alert(a)
alert(a.push(6)) script><script> <BR></script>

unshift method
Inserts the specified element into the beginning of the array and returns the array.

arrayObj.unshift([item1[, item2 [, . . . [, itemN]]]])

Parameters
arrayObj

Required. An Array object.

item1, item2,. . .,itemN

Optional. The element to be inserted at the beginning of this Array.

Explanation The
unshift method inserts these elements into the beginning of an array, so these elements will appear in the array in the order of the parameter sequence.

Copy code The code is as follows:

Array.prototype.unshift=function(){   
     var len=arguments.length;   
     this.reverse();   
     if(len>0)for(var i=len;i>0;i--)this[this.length]=arguments[i-1];   
     return this.reverse();   
     }   
var a=[1,2,3,4]   
a.unshift()   
alert(a)   
a.unshift(5,6)   
alert(a)   
alert(a.unshift(7))

splice 方法  
从一个数组中移除一个或多个元素，如果必要，在所移除元素的位置上插入新元素，返回所移除的元素。  

arrayObj.splice(start, deleteCount, [item1[, item2[, . . . [,itemN]]]])  

参数  
arrayObj  

必选项。一个 Array 对象。  

start  

必选项。指定从数组中移除元素的开始位置，这个位置是从 0 开始计算的。  

deleteCount  

必选项。要移除的元素的个数。  

item1, item2,. . .,itemN  

必选项。要在所移除元素的位置上插入的新元素。  

说明  
splice 方法可以移除从 start 位置开始的指定个数的元素并插入新元素，从而修改 arrayObj。返回值是一个由所移除的元素组成的新 Array 对象。  

复制代码 代码如下:

alert(a.splice(0,1));   
alert(a.splice(0,1,1,1,1,1,1,1,1))   
<script>    <BR>Array.prototype.shift=function(){    <BR>     var f=this[0];    <BR>     for(var i=0;i<this.length;i )this[i]=this[i 1];    <BR>     this.length--;    <BR>     return f;    <BR>     }    <BR></script>

  
shift 方法  
移除数组中的第一个元素并返回该元素。  

arrayObj.shift( )  

必选的 arrayObj 引用是一个 Array 对象。  

说明  
shift 方法可移除数组中的第一个元素并返回该元素。  

复制代码 代码如下:

var a=[1,2]   
alert(a.shift())   
alert(a)