How to Clamp Numbers in JavaScript

Use the following function in JavaScript to easily clamp numbers between a min and a max value:

const min = 0;
const max = 100;

// Clamp number between two values with the following line:
const clamp = (num, min, max) => Math.min(Math.max(num, min), max);

clamp(-50, min, max); // Will return: 0
clamp(50, min, max);  // Will return: 50
clamp(500, min, max); // Will return: 100
Copied to clipboard!
JavaScript Course


Let's break this code down to fully understand what is going on. You start with a number, and min and max values. Let's say the number you want to cap is 50, your min is 0, and your max is 100. You pass your number to Math.max, along with your min value:

Math.max(50, 0); // -> 50
Copied to clipboard!

This will return the higher number from the two, which means you get 50 back. You then pass this to Math.min along with your max value:

Math.min(50, 100); // -> 50
Copied to clipboard!

This time, this will return the lowest number from the passed arguments. Hence:

Remove ads


Using the same function, you could make it global by extending the Number object:

Number.prototype.clamp = (num, min, max) => Math.min(Math.max(num, min), max);

(-50).clamp(-50, min, max);
(50).clamp(50, min, max);
(500).clamp(500, min, max);
Copied to clipboard!

However, keep in mind this is considered to be a bad practice and should be avoided. Only use it if you need compatibility with newer features.

You should not extend native prototype, unless it is for compatibility reasons.
As stated in the Conclusion section on MDN (Inheritance & prototype chain)

Instead, if you use a modern framework, you can simply include it at the root of your project or store it in a global namespaced object. (eg.: app.utils.clamp)

There is also a proposal for a built in Math.clamp function, however, it is still in draft. Until it gets widely adopted, you need to polyfill it.

How to Clamp Numbers in JavaScript
If you would like to see more Webtips, follow @flowforfrank


Remove ads
Remove ads

๐Ÿ“š Get access to exclusive content

Want to get access to exclusive content? Support webtips with the price of a coffee to get access to tips, checklists, cheatsheets, and much more. โ˜•

Get access Support us
Remove ads
Remove ads
Remove ads
๐ŸŽ‰ Thank you for subscribing to our newsletter. x This site uses cookies We use cookies to understand visitors and create a better experience for you. By clicking on "Accept", you accept its use. To find out more, please see our privacy policy.