Your version of Safari most likely lacks support for ES6 features like arrow functions[0], you could use babel[1] to transpile the code to ES5:

  (function (f) {
    return f(f);
  })(function (func) {
    return function (n) {
      return n === 0 ? 1 : n * func(func)(n - 1);
    };
  })(19);

[0] http://caniuse.com/#feat=arrow-functions

[1] https://babeljs.io/repl/