SwiftToJavascript.swift

//Import Javascript core
import JavaScriptCore

//[...]

//Get the JS Context
let context = JSContext()!

//write your function in javascript and feed it to context
context.evaluateScript(#"""
    function chompLeft(fullString,separator) {

        let index = fullString.lastIndexOf(separator);
               if(index == -1)
                {
                    return undefined;
                }
       return fullString.substring(index+1+separator.length,fullString.length);

    }
    """#);
//get the function back from javascript to swift
let splitString = context.objectForKeyedSubscript("chompLeft")!

//call the method with parameters
let result = splitString.call(withArguments: ["hello world!","hello"])!.toString();

//done
print(result);


//for more string operations in javascript:
//https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String