as amber and sinan have noted above, the javascritp '.split' method will work just fine. Just pass it the string separator(-) and the string that you intend to split('123-abc-itchy-knee') and it will do the rest.
var coolVar = '123-abc-itchy-knee';
var coolVarParts = coolVar.split('-'); // this is an array containing the items
var1=coolVarParts[0]; //this will retrieve 123
To access each item from the array just use the respective index(indices start at zero).