Some handy Javascript array methods

Working with javascript arrays today, I found some handy functions:

- Creating an array :
var ray = [];

- Joining two arrays :
var resultArray = ArrayOne.concat(ArrayTwo);

- Getting only unique items in an array :
(Jquery has a unique function, but it does not work on strings / numbers)

Array.prototype.unique = function() {
var result = new Array();
o: for (var i = 0, n = this.length; i < n; i++) {
for (var x = 0, y = result.length; x < y; x++) {
if (result[x] == this[i]) {
continue o;
}
}
result[result.length] = this[i];
}
return r;
}

- For each in JavaScript(using JQuery):
(although JavaScript has for (item in collection) functionality, it is not useful as it also iterates through the methods of the object.)

$.each(collection, function(index, value) { alert(index + ' : ' + value); });

- Bonus JavaScript : Splitting a string by multiple delimiters :
use a regular expression :
var result = myString.split(/[DELIMITERS]+/);
just replace DELIMITERS with the delimiters you want (one character delimiters)

Good old VB functions in c# Left, Mid, Right

Missing the good old string functions in c# I wanted to recreate them.
This is my solution where they are resurrected as extension methods.

public static class StringHelper
{
    public static string Right(this String source, int length)
    {
        if (source.Length == 0 || length <= 0)
        {
        return "";
        }

        return source.Substring(source.Length - length, length);
    }

    public static string Left(this String source, int length)
    {
        if (source.Length == 0 || length <= 0)
        {
        return "";
        }

        return source.Substring(0, length);
    }

    public static string Mid(this string source, int startIndex, int length)
    {
        if (source.Length == 0 || length <= 0 || startIndex < 0)
        {
        return "";
        }
        return source.Substring(startIndex, length);
    }

    public static string Mid(this string source, int startIndex)
    {
        if (source.Length == 0 || startIndex < 0)
        {
        return "";
        }
        return source.Substring(startIndex);
    }
}

To keep the code from giving errors I check for the length parameter,
if this is not what you want, you can throw an argumentexception for example ...