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Eckehard

Posted on • Updated on

# Easy Math in Javascript

Javascript provides a Math-object, that covers a broad range of useful constants and functions. However, sometimes it may happen, your are missing a function or the builtin function does not provide what you need. And - not everybody is happy that all Math-functions need to be prefixed by the word "Math". But luckily, Javascript is a flexible language and there is some help.

### Extending the "Math"-object

Actually, it can be seen as a weak point, that Javascript objects do not have any access protection. In our current case, this is an advantage. You can easily add new functions to the "Math"-object or even change the inbuilt ones. Here is an example of the round()-function, that does not allow to set decimals. But this can be easily fixed:

Math._round = Math.round
Math.round = (f, n = 0) => {
let m = Math.pow(10, n)
return (Math._round(f * m) / m)
}

Here, we store the initial round function in a new property called _round. Then we can overwrite the initial property with a new function.

We can also extend the Math-object with some useful stuff:

Math.PI2 = 2*Math.PI

// Range-Check: True if x in Range (L .. H)
Math.inRange = (x, L, H) => (x < L) ? false : x <= H

// Constrain value: Limit x to range (L .. H)
Math.constrain = (x, L, H) => x < L ?  L : x > H ? H : x

The new functions work seamlessly as if they where inbuilt.

### Math destructuring

So, and how to get rid of the Math-prefix? You can use object
destructuring here:

let {sin, cos, round, inRange, constrain, PI, PI2} = Math

Now the functions are available in the global scope:

round(sin(0.1*PI2),3) // -> 0.588
inRange(3.158,2,4) // -> true
constrain(3.158,4,5) // -> 4

You can play around with the code in flems.io