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JavaScript Object-Oriented JavaScript (2015) Constructor Functions and Prototypes Methods with Prototypes

Posted by john larson
john larson
16,594 Points

How is "Dice.prototype.roll" more efficient than "function diceRoll"

We went through a lot of cajoling to get to this point so my question is this:

// how is this
Dice.prototype.roll = function(){
        var randomNumber = Math.floor(Math.random() * this.sides) + 1;
        return randomNumber;
}
// any more efficient than this
function diceRoll(){
    var randomNumber = Math.floor(Math.random() * sides) + 1;
        return randomNumber;
}

1 Answer

Steven Parker
Steven Parker
231,275 Points
Steven Parker
Steven Parker
231,275 Points

:point_right: Prototype function code is shared among all instances.

If you encode a method directly in the constructor, all instances of that class will have their own copy of of the method code.

By using the prototype to define the method, all instances will share the same bit of code, saving on memory and instantiation time.

john larson
john larson
16,594 Points

Thanks Steve. I don't fully grasp that, but it's enough of the tip of the iceberg to hold on to.