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JavaScript Object-Oriented JavaScript (2015) Introduction to Methods Returning Values

I don't understand this part: var result = dice.roll();

at 1:50 on the video, Andrew changes var result = 1; to var result = dice.roll(); I thought I have to bring the whole variable into var result like this. var result = var dice; variable can't have another variable as a property?

Wesley Pak
Wesley Pak
4,277 Points

Remember from the previous video that we had created inside the object, 'dice', well there was a function inside it named roll, that is where it came from. dice.roll is not a variable. it is just a function inside a variable, you dont have to use the this method on it, by saying just the name, it does the same thing. Boom 10 year child solved the case.

2 Answers

Aaron Price
Aaron Price
5,974 Points

I haven't been following the series, but I'm pretty sure I can guess what's tripping you up. It's a lot deeper than you might expect, but if you can master this it'll take you far! Consider the following:

// In the following code, we ask for the value of bar. You get an error: "Bar wasn't DEFINED". One of the bad parts of js is that in this case it SHOULD say "not DECLARED", but doesn't. It says "not DEFINED".


// Here we DECLARE bar without DEFINING it.

var bar

// Here we ask for the VALUE of bar again. It's undefined but not an error, because it was already DECLARED


// Here we DECLARE foo, and DEFINE it by ASSIGNING it to a VALUE

var foo = "hello"

// Here we ask for the VALUE of foo, and get back the string "hello"


// Here we're trying to DECLARE two different variables. That doesn't make sense, and will error

var arr = var foo

// Here we DECLARE arr and DEFINE it by ASSIGNING it to the VALUE of foo, which is the string "hello"

var arr = foo

// Therefore, asking for the value of arr will return the string "hello"


Now your question was similar, just with objects and functions. Side note on semantics: a method is just a function attached to an object. Note that calling a function or method by it's name will return the function itself. Calling it with parenthesis attached will give the RETURN VALUE of the function.

// Let's define the object dice

dice = {

roll: function() { return 42; }


// Here we ask for the OBJECT dice. It is { roll: function(){ return 42; } }


// Here we ask for the RETURN VALUE of the method roll. It is 42.


// Here we ask for the method itself. It is function() { return 42; }


//Now finally your answer should be clearer. The following gives an error, you're trying to declare two things at once

var result = var dice

// Below, result is assigned to the object itself.

var result = dice

// below, we ask for the value of result, which is an object. { roll: function(){ return 42; } }


// Next, result is reassigned to the method itself.

var result = dice.roll

// We call it, get back the value, which is a function. function(){ return 42; }


// Finally, result is reassigned to the RETURN VALUE of the method.

var result = dice.roll()

// we call result, and get back the number 42.


Neil McPartlin
Neil McPartlin
14,662 Points

Aaron Price, take a bow. Nice work.

...but if you can master this it'll take you far!

Oh so true. Many thanks.

Rafael de Oliveira
Rafael de Oliveira
11,174 Points

"dice" is a object. "roll()" is a function of the object (a method). So, "dice.roll()" will give you a number automatically.