Js-array using Notes

The use of array arrays in JS {reprint}

JS array element Additions and deletions have 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; 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: Adds a parameter to the beginning of the original array and returns 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 can be used instead of this method.

Pop: Deletes the last item of the original array and returns the value of the deleted element; 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//You don't have to return, you can call it directly.

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,...

When emptying an array, simply pass the startindex.

If you do not delete all the elements, then pass the DeleteCount parameter.

Splice also has the ability to add after the first deletion, that is, to delete several elements, and then add several elements in the deleted position, the number of deleted and added elements do not have to be equal, then Hou DeleteCount is also used.
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 if omitted
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);
}

Js-array using Notes