phpjs/functions/math/tanh.js

php.js offers community built php functions in javascript

function tanh(arg) {
  // From: http://phpjs.org/functions
  // +   original by: Onno Marsman
  // *     example 1: tanh(5.4251848798444815);
  // *     returns 1: 0.9999612058841574
  return (Math.exp(arg) - Math.exp(-arg)) / (Math.exp(arg) + Math.exp(-arg));
}