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;
    }
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.