var partial = function() {
      const fn = arguments[0];
      const slice = Array.prototype.slice;
      const args = slice.call(arguments, 1);

      // Return a function that calls fn
      return function() {
        var remainingArgs = slice.call(arguments);
        return fn.apply(this, args.concat(remainingArgs));
      }
    }
    // test case
    const add = (a, b) => a + b;
    const add3 = partial(add, 3)
    console.log(add3(1))
    console.log(add3(4))