function add (a, b) {
    return a + b;
}
function multiply (a, b) {
    return a * b;
}
function applyFn (fn) {
    var parentArgs = Array.prototype.slice.call(arguments, 0);
    function wrapper () {
        var args = parentArgs.slice(1);
        args = args.concat(Array.prototype.slice.call(arguments, 0));
        
        if (args.length >= 2) {
            return fn.apply(this, args);
        }
        
        return applyFn.apply(this, parentArgs.concat(args));
    }
    return arguments.length-1 >= 2 ? wrapper() : wrapper;
}
var f = applyFn(multiply);
console.log('3x5', f(3)(5));
console.log('2x8', f(2)(8));
f = applyFn(add);
console.log('3+5', f(3)(5));
console.log('2+8', f(2)(8));
console.log('2+8', f(2)(8)(10));