javascript - Why is Math.prototype undefined? - Stack Overflow

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I must be missing something here, because Math.prototype is undefined for me. Why is this? I tried to do something like this:

Math.prototype.randomRange = function(from, to){
    return Math.floor(Math.random() * (to - from + 1) + from);
}

But instead had to do something like this:

Math.randomRange = function(from, to){
    return Math.floor(Math.random() * (to - from + 1) + from);
}

That doesn't feel right, though. Is it just me or should I be doing this another way? I apologize if this is a silly or duplicate question, but I couldn't find anything by searching (exactly two questions turn up when I search SO for "Math.prototype", which is kind of weird).

I must be missing something here, because Math.prototype is undefined for me. Why is this? I tried to do something like this:

Math.prototype.randomRange = function(from, to){
    return Math.floor(Math.random() * (to - from + 1) + from);
}

But instead had to do something like this:

Math.randomRange = function(from, to){
    return Math.floor(Math.random() * (to - from + 1) + from);
}

That doesn't feel right, though. Is it just me or should I be doing this another way? I apologize if this is a silly or duplicate question, but I couldn't find anything by searching (exactly two questions turn up when I search SO for "Math.prototype", which is kind of weird).

• javascript
• math
• prototype

Share Improve this question Follow asked May 30, 2012 at 16:40 Elliot BonnevilleElliot Bonneville 53.4k2323 gold badges100100 silver badges124124 bronze badges 3

• Please read this good advice – Denys Séguret Commented May 30, 2012 at 16:44
• @dystroy: I am well aware of the caveats surrounding extending built-in objects. I appreciate the link anyhow, though. --edit-- You appear to be referring to extending prototypes, which I'm not doing. – Elliot Bonneville Commented May 30, 2012 at 16:45
• 1 Simple: function objects (constructors) have prototypes, Math is not a constructor function. typeof Math returns "object", but typeof Array returns "function". – doug65536 Commented Sep 26, 2016 at 20:58

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3 Answers 3

Sorted by: Reset to default 6

The Math functions are like class-level functions in other OO languages. There's no prototype object on the constructor; nobody (I know of) uses the constructor anyway. (What would you do with a Math instance?)

edit — it's been pointed out in a ment (and it never occurred to me to check I guess) that Math isn't a function anyway. Type Math() in your browser console and you'll get an error.

Math in JavaScript is the equivalent of a static class in other languages. It has no prototype or constructor (the equivalent of, say, writing a class in Java with all static methods and only a private constructor).

For further information, see this StackOverflow question: Is there any practical use of redefining Math.constructor in JavaScript/ActionScript?

Specifically, the accepted answer: https://stackoverflow./a/10431309/1403635

Because Math is a static object, not a constructor. It will throw an error if you call new Math()

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