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

Posted by john larson
john larson
16,594 Points

If I use button for dice.roll() i get error dice.roll is not a function. If I print dice directly to the page it's ok

Directly to the page this works fine

function print(output){
    document.getElementById("display").innerHTML = output;
}

var button = document.getElementById("button");

var dice = {
    sides: 6,
    roll: function(){
        var randomNumber = Math.floor(Math.random() * this.sides) + 1;
        return randomNumber;
    }
}
print(dice.roll());

If I use this button I get the error dice.roll is not a function

button.onclick = function(){
    var result = dice.Roll();
    print(result);
}
john larson
john larson
16,594 Points

It's when I click on the button that I get the error. So I gather that means the problem is in the function/onclick event itself...but I don't see it.

<button id="button">Roll the Dice</button>
john larson
john larson
16,594 Points

Thanks to both of you. You guys were neck and neck on that one. If it would have been a horse race it would have been a photo finish.

john larson
john larson
16,594 Points

I must remind myself of the three S's: Syntax, Spelling and caseSensitive. It's often one of those three that catch me up.

2 Answers

Steven Parker
Steven Parker
229,785 Points
Steven Parker
Steven Parker
229,785 Points

:point_right: dice.Roll was never defined. It is not a function.

But dice.roll (with lower-case "r") is.

Remember that JavaScript is case-sensitive.

john larson
john larson
16,594 Points

oh yeah, now I see it.

Kristian Gausel
Kristian Gausel
14,661 Points
Kristian Gausel
Kristian Gausel
14,661 Points

Try:

button.onclick = function(){
    var result = dice.roll();
    print(result);
}

JavaScript is case sensitive, and you're doing it right in the "print" example ;)

john larson
john larson
16,594 Points

I copy and pasted yours below mine. They look exactly the same to me but yours works. What am I not seeing?

Kristian Gausel
Kristian Gausel
14,661 Points
Kristian Gausel
Kristian Gausel
14,661 Points

the lowercase 'r' in 'dice.roll'

Steven Parker
Steven Parker
229,785 Points
Steven Parker
Steven Parker
229,785 Points

"R" vs. "r"

(Uppercase vs. lowercase.)