From http://www.w3schools.com (Copyright Refsnes Data)

WMLScript removeAt() Function

The removeAt() function divides a string into elements and removes a specified element.

Syntax

n = String.removeAt(string, index, separator)

Part	Description
n	The string returned from the function
string	The original string
index	The index of the element to be removed
separator	The dividing separator

Example

var a = String.removeAt("Visit W3Schools!",0," ");
var b = String.removeAt("Visit W3Schools!",0,"W");
var c = String.removeAt("Visit W3Schools!",-2," ");
var d = String.removeAt("Visit W3Schools!",10," ");

Result

a = "W3Schools!"
b = "3Schools!"
c = "W3Schools!"
d = "Visit"

Complete WMLScript String Library