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JavaScript Object-Oriented JavaScript (2015) Constructor Functions and Prototypes Make a Constructor Challenge

Posted by Bryan Woodard
Bryan Woodard
5,757 Points

Why does this work and not the other?

Why does this code return undefined when dice10.roll() is called?

function dice(sides){ this.sides = sides; this.roll = function (){ console.log( Math.floor(Math.random() * this.sides) + 1); };
}

var dice10 = new dice(10);

dice10.roll();

but this one actually works

function dice(sides){ this.sides = sides; this.roll = function (){ return Math.floor(Math.random() * this.sides) + 1; };
}

var dice10 = new dice(10);

dice10.roll();

1 Answer

Paul Cox
Paul Cox
12,671 Points
Paul Cox
Paul Cox
12,671 Points

The accepted answer is incorrect. The first example doesn't return the roll value in the roll function, it logs it to the console. A function returns undefined if a value was not returned. Therefore, when running the code in the console, the 1st example will display the roll value then undefined in the console, whereas the 2nd example will only display the roll value.