phpjs/functions/math/acosh.js

php.js offers community built php functions in javascript

function acosh(arg) {
  // From: http://phpjs.org/functions
  // +   original by: Onno Marsman
  // *     example 1: acosh(8723321.4);
  // *     returns 1: 16.674657798418625
  return Math.log(arg + Math.sqrt(arg * arg - 1));
}