lodash/internal/createBaseWrapper.js

define(['./createCtorWrapper', './root'], function(createCtorWrapper, root) {

  /** Used to compose bitmasks for wrapper metadata. */
  var BIND_FLAG = 1;

  /**
   * 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 of wrapper flags. See `createWrapper` for more details.
   * @param {*} [thisArg] The `this` binding of `func`.
   * @returns {Function} Returns the new wrapped function.
   */
  function createBaseWrapper(func, bitmask, thisArg) {
    var isBind = bitmask & BIND_FLAG,
        Ctor = createCtorWrapper(func);

    function wrapper() {
      var fn = (this && this !== root && this instanceof wrapper) ? Ctor : func;
      return fn.apply(isBind ? thisArg : this, arguments);
    }
    return wrapper;
  }

  return createBaseWrapper;
});