Using split/join to replace a string with an array

I'm trying to replace the value of item with values ​​in the array arr, but I only get that if I use: arr [1], arr [2] ... if I just let arr, returns abcdefg.

I am PHP programmer, and I have a minimal notion wit开发者_运维百科h JavaScript, can someone give me a light?

var item = 'abcdefg';
var arr = new Array();
arr[1] = "zzz";
arr[2] = "abc";
var test = item.split(arr);
alert(test.join("\n"));

Use:

var item = 'Hello, 1, my name is 2.';
var arr = new Array();
arr [1] = 'admin';
arr [2] = 'guest';
for (var x in arr)
    item = item.replace(x, arr[x]);
alert(item);

It produces:

Hello, admin, my name is guest.

Split uses regular expressions, so

"My String".split('S') == ["My ","tring"]

If you are trying to replace a string:

"abcdef".replace('abc','zzz') == "zzzdef"