phpjs/functions/math/tan.js

php.js offers community built php functions in javascript

function tan(arg) {
  // From: http://phpjs.org/functions
  // +   original by: Onno Marsman
  // *     example 1: tan(8723321.4);
  // *     returns 1: 5.4251848798448234
  return Math.tan(arg);
}