JS array Methods summarize array element additions and deletions-yuzhongwusan-Blog Park

<title>JS array Methods summarize array element additions and deletions-yuzhongwusan-Blog Park</title>

js array elements of the addition and deletion has been confused, today finally found the details of the information, first give me a test code ^-^
var arr = new Array ();
arr[0] = "AAA";
arr[1] = "BBB";
arr[2] = "CCC";
//alert (arr.length);//3
Arr.pop ();
//alert (arr.length);//2
//alert (arr[arr.length-1]);//BBB
Arr.pop ();
//alert (arr[arr.length-1]);//AAA
//alert ( arr.length);//1

var arr2 = new Array ();
alert (arr2.length);//0
Arr2[0] = "AAA";
ARR2[1] = "BBB";
alert (arr2.length);//2
Arr2.pop ();
alert (arr2.length);//1
ARR2 = Arr2.slice (0,arr2.length-1);?
alert (arr2.length);//0
Arr2[0] = "AAA";
ARR2[1] = "BBB";
ARR2[2] = "CCC";
ARR2 = Arr2.slice (0,1);?
alert (arr2.length);//1
Alert (arr2[0]);//aaa
Alert (arr2[1]);//undefined

Shift: Deletes the first item of the original array and returns the value of the deleted element, or returns undefined if the array is empty?
var a = [1,2,3,4,5];?
var B = A.shift (); a:[2,3,4,5]?? B:1?

Unshift: Add parameters to the beginning of the original array and return the length of the array?
var a = [1,2,3,4,5];?
var B = A.unshift ( -2,-1); a:[-2,-1,1,2,3,4,5]?? B:7?
Note: The test return value under IE6.0 is always undefined,ff2.0 Test return value is 7, so the return value of this method is not reliable, need to use the return value when the splice instead of this method to use.

Pop: Deletes the last item of the original array and returns the value of the deleted element, or returns undefined if the array is empty?
var a = [1,2,3,4,5];?
var B = A.pop (); a:[1,2,3,4]?? B:5//Do not return the words directly to call on it.

Push: Adds a parameter to the end of the original array and returns the length of the array?
var a = [1,2,3,4,5];?
var B = A.push (6,7); a:[1,2,3,4,5,6,7]?? B:7?

Concat: Returns a new array that consists of adding parameters to the original array?
var a = [1,2,3,4,5];?
var B = A.concat (6,7); a:[1,2,3,4,5]?? b:[1,2,3,4,5,6,7]?

Splice (Start,deletecount,val1,val2,...) : Deletes the DeleteCount entry starting from the start position and inserts the Val1,val2 from that position,...?
var a = [1,2,3,4,5];?
var B = A.splice (2,2,7,8,9); a:[1,2,7,8,9,5]?? b:[3,4]?
var B = a.splice (0,1); With shift?
A.splice (0,0,-2,-1); var B = a.length; With Unshift?
var B = A.splice (a.length-1,1); With pop?
A.splice (a.length,0,6,7); var B = a.length; With push?

Reverse: Reverse the array?
var a = [1,2,3,4,5];?
var B = A.reverse (); a:[5,4,3,2,1]?? b:[5,4,3,2,1]?

Sort (orderfunction): Sorts the array by the specified parameters?
var a = [1,2,3,4,5];?
var B = A.sort (); a:[1,2,3,4,5]?? b:[1,2,3,4,5]?

Slice (Start,end): Returns a new array that consists of the entries from the original array that specify the starting subscript to the end subscript?
var a = [1,2,3,4,5];?
var B = a.slice (2,5); a:[1,2,3,4,5]?? b:[3,4,5]?

Join (Separator): Sets the element group of the array as a string, separator as a delimiter, or by default with a comma delimiter?
var a = [1,2,3,4,5];?
var B = A.join ("|"); a:[1,2,3,4,5]?? B: "1|2|3|4|5"

Another way to manipulate strings using the array emulation Javastringbuffer:

/**
* String processing function
*/
function StringBuffer ()
{
var arr = new Array;
This.append = function (str)
{
??? Arr[arr.length] = str;?
};

this.tostring = function ()
{
??? Return Arr.join ("");? Ping the append incoming array into a string
};
}

In the application today, it is suddenly found that join is a good way to convert an array into a string, so it is encapsulated into objects using:

/**
* Convert an array into a string of specific symbol splits
*/
function arraytostring (arr,separator)
{
if (!separator) separator = "";//separator is null default is NULL
??? return Arr.join (separator);?
}

/**
* Find the string contained in the array
*/
function arrayfindstring (arr,string)
{
var str = arr.join ("");?
??? return Str.indexof (string);?
}

From for notes (Wiz)

JS array Methods summarize array element additions and deletions-yuzhongwusan-Blog Park