Ruby's Math.acos in JavaScript

Here’s what our current JavaScript equivalent to Ruby's Math.acos looks like.

module.exports = function acos (arg) {
// discuss at:
// original by: Onno Marsman (
// note 1: Sorry about the crippled test.
// note 1: Needed because precision differs accross platforms.
// example 1: (acos(0.3) + '').substr(0, 17)
// returns 1: '1.266103672779499'
return Math.acos(arg)
[ View on GitHub | Edit on GitHub | Source on GitHub ]

How to use

You you can install via npm install locutus and require it via require('locutus/ruby/Math/acos'). You could also require the Math module in full so that you could access Math.acos instead.

If you intend to target the browser, you can then use a module bundler such as Parcel, webpack, Browserify, or rollup.js. This can be important because Locutus allows modern JavaScript in the source files, meaning it may not work in all browsers without a build/transpile step. Locutus does transpile all functions to ES5 before publishing to npm.

A community effort

Not unlike Wikipedia, Locutus is an ongoing community effort. Our philosophy follows The McDonald’s Theory. This means that we don't consider it to be a bad thing that many of our functions are first iterations, which may still have their fair share of issues. We hope that these flaws will inspire others to come up with better ideas.

This way of working also means that we don't offer any production guarantees, and recommend to use Locutus inspiration and learning purposes only.


  • Sorry about the crippled test. Needed because precision differs accross platforms.


Please note that these examples are distilled from test cases that automatically verify our functions still work correctly. This could explain some quirky ones.

#codeexpected result
1(acos(0.3) + '').substr(0, 17)'1.266103672779499'

Ehm.. Only 1 Ruby function in all of Locutus?

We could still assimilate many more functions to this language. We only just rolled out multilingual support to Locutus. If you fancy a challenge, we'd love your help expanding that. For instance, you could:

  • Get inspiration from the Ruby core documentation.
  • Click "New file" in the appropriate folder on GitHub. This will fork the project to your account, directly add the file to it, and send a Pull Request to us.

We will then review it. If it's useful to the project and in line with our contributing guidelines your work will become part of Locutus and you'll be automatically credited in the authors section accordingly.

« More Ruby Math functions