isStrictFunction

isStrictFunction.js

function isStrictFunction(fn) {
  if (typeof fn != 'function') throw "Not a function";
  try {
    fn.caller, fn.arguments;
    return false;
  } catch (e) {
    return e instanceof TypeError;
  }
}

(function () {
  "use strict";
  function fd() {}

  console.log(isStrictFunction(fd));                        // true
  console.log(isStrictFunction(function(){}));              // true
  console.log(isStrictFunction(Function("'use strict'")));  // true
  console.log(isStrictFunction(Function()));                // false
  console.log(isStrictFunction(isStrictFunction));          // false
})();