JS Array method summarizes the addition and deletion of array elements

JS array element Additions and deletions have been confused, today finally found detailed 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 var a = [1,2,3,4,5] If the array is empty; 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 the return value is 7, so the return value of this method is not reliable and needs to be used when the return value is splice instead of this method.
Pop: Deletes the last item of the original array andReturns the value of the deleted element, or returns undefined var a = [1,2,3,4,5] If the array is empty; 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, which is the var a = [1,2,3,4,5] That is added to the original array; 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 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 to 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 of 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 handler 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 to a specific symbol split String */function arraytostring (arr,separator) {if (!separator) separator = "";//          Separator is null, the default is null return Arr.join (separator); }

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

JS Array method summarizes the addition and deletion of array elements