function prefix(initFn, mainFn) {
    return function(){
        var func = initFn;
        initFn = mainFn;
        return func.apply(this, arguments);
    }
}

function add(a, b){
    return a + b;
}

function multiply(a, b){
    return a * b;
}

var addThenMultiply = prefix(add, multiply);

console.log(addThenMultiply(2, 3)); // => 5
console.log(addThenMultiply(2, 3)); // => 6
console.log(addThenMultiply(2, 3)); // => 6