code: function createBind(func, bitmask, thisArg) {
        var isBind = bitmask & WRAP_BIND_FLAG,
            Ctor = createCtor(func);
  
        function wrapper() {
          var fn = (this && this !== root && this instanceof wrapper) ? Ctor : func;
          return fn.apply(isBind ? thisArg : this, arguments);
        }
        return wrapper;
      }
docs: Creates a function that wraps `func` to invoke it with the optional `this`
  binding of `thisArg`.
  
  @private
  @param {Function} func The function to wrap.
  @param {number} bitmask The bitmask flags. See `createWrap` for more details.
  @param {*} [thisArg] The `this` binding of `func`.
  @returns {Function} Returns the new wrapped function.