Add the decorating "defer()" to functions

back to the lesson

Add to the prototype of all functions the method defer(ms), that returns a wrapper, delaying the call by ms milliseconds.

Here’s an example of how it should work:

          function f(a, b) {
  alert( a + b );
}

f.defer(1000)(1, 2); // shows 3 after 1 second
        

Please note that the arguments should be passed to the original function.

Function.prototype.defer = function(ms) {
  let f = this;
  return function(...args) {
    setTimeout(() => f.apply(this, args), ms);
  }
};

// check it
function f(a, b) {
  alert( a + b );
}

f.defer(1000)(1, 2); // shows 3 after 1 sec

Please note: we use this in f.apply to make our decoration work for object methods.

So if the wrapper function is called as an object method, then this is passed to the original method f.

Function.prototype.defer = function(ms) {
  let f = this;
  return function(...args) {
    setTimeout(() => f.apply(this, args), ms);
  }
};

let user = {
  name: "John",
  sayHi() {
    alert(this.name);
  }
}

user.sayHi = user.sayHi.defer(1000);

user.sayHi();