_createCtor.js

define(['./_baseCreate', './isObject'], function(baseCreate, isObject) {

  /**
   * Creates a function that produces an instance of `Ctor` regardless of
   * whether it was invoked as part of a `new` expression or by `call` or `apply`.
   *
   * @private
   * @param {Function} Ctor The constructor to wrap.
   * @returns {Function} Returns the new wrapped function.
   */
  function createCtor(Ctor) {
    return function() {
      // Use a `switch` statement to work with class constructors. See
      // http://ecma-international.org/ecma-262/7.0/#sec-ecmascript-function-objects-call-thisargument-argumentslist
      // for more details.
      var args = arguments;
      switch (args.length) {
        case 0: return new Ctor;
        case 1: return new Ctor(args[0]);
        case 2: return new Ctor(args[0], args[1]);
        case 3: return new Ctor(args[0], args[1], args[2]);
        case 4: return new Ctor(args[0], args[1], args[2], args[3]);
        case 5: return new Ctor(args[0], args[1], args[2], args[3], args[4]);
        case 6: return new Ctor(args[0], args[1], args[2], args[3], args[4], args[5]);
        case 7: return new Ctor(args[0], args[1], args[2], args[3], args[4], args[5], args[6]);
      }
      var thisBinding = baseCreate(Ctor.prototype),
          result = Ctor.apply(thisBinding, args);

      // Mimic the constructor's `return` behavior.
      // See https://es5.github.io/#x13.2.2 for more details.
      return isObject(result) ? result : thisBinding;
    };
  }

  return createCtor;
});