To test against null you should use the operator !== instead of !=
If (this.rawValue !== null) {
this.rawValue = "/ " + this.rawValue;
}
Well, this propably wont avoid the slash gets repeated because the script will add an extra slash every time it is fired.
You'll need to check the current value for an slash atthe beginning using a regular expression like:
/^\//g
The script the could like like:
If (this.rawValue !== null) {
If (!this.rawValue.match(/^\//g)) {
this.rawValue = "/ " + this.rawValue;
}
}