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JavaScript

Posted by Douglas Watts
Douglas Watts
5,464 Points

Javascript Objects

This Challenge is way beyond me, does anyone understand and could you please explain:

var genericGreet = function(name, mood) {
        name = name || "you";
        mood = mood || "good";
        return "Hello " + name + ", my name is " + this.name +
          " and I am in a " + mood + " mood!";
      }

      var andrew = {
        name: "Andrew"
      }

      var args1 = ["Michael", "awesome", ":)"];

      var greeting = genericGreet;

thanks.

tihomirvelev
tihomirvelev
14,109 Points

Hello,

If you type the text/question of the challenge it will be much easier to help. :)

3 Answers

tihomirvelev
tihomirvelev
14,109 Points

Well...let me try to explain it with my broken English. :)

The answer is:

var greeting = genericGreet.apply(andrew, args1);

The basic task is to replace the variables name , mood and this.name in the var genericGreet in the first line of the code.

To do that you can use 2 methods - call() or apply().

The only basic difference between the two methods is that with apply() you can pass in an array of arguments as an argument but with call() you have to write manually every single argument.

Since in the challenge you have to use the array args1, then you must use apply().

apply() takes up two arguments - the first is the context and the second is the array.

The context is simply what will be replaced each time when there is this.name or any other type of that. So if there is this.something it will be replaced with the context.

So in the challenge you are passing the object andrew as a context. That way, in the function of the top of the code, this.name will be replaced with andrew.name. And since andrew.name = "Andrew", his name will be displayed in that place.

The second argumet is the array args1. The first element is "Michael", the second is "awesome" and the third is ":)".

You can see that the top page function takes up two arguments - name and mood.

Therefore name = Michael and mood = awesome. The third element in the array is just to fool you. It's not gonna actually be used in the function because the function takes only two arguments.

That's the basic explanation and I hope it helps. At first it might be confusing but watch Jim's video a few more times and you will understand it: http://teamtreehouse.com/library/javascript-foundations/objects/call-and-apply

Good luck!

Derick Moncado
Derick Moncado
23,259 Points

Thanks man! Really helpful!

Brian van Vlymen
Brian van Vlymen
12,637 Points

wow it was excellent explain! I would like to take other challenge using call to see the diff between apply and call method.

Michael Hicks
Michael Hicks
24,208 Points
Michael Hicks
Michael Hicks
24,208 Points

Fantastic explanation! Thank you tihomirvelev.

Douglas Watts
Douglas Watts
5,464 Points
Douglas Watts
Douglas Watts
5,464 Points

Sorry, i forgot to include the challenge text, so i will start over...Could someone please help with this Challenge:

Set the 'greeting' variable, on line 29, by using the 'genericGreet' function in the context of 'andrew' with the array of arguments, 'args1'.

var genericGreet = function(name, mood) {
        name = name || "you";
        mood = mood || "good";
        return "Hello " + name + ", my name is " + this.name +
          " and I am in a " + mood + " mood!";
      }

      var andrew = {
        name: "Andrew"
      }

      var args1 = ["Michael", "awesome", ":)"];

      var greeting = genericGreet;

thanks.

Douglas Watts
Douglas Watts
5,464 Points
Douglas Watts
Douglas Watts
5,464 Points

Thanks, your English was perfect and i will go over the video a couple more times.