function bind(func, thisArg) {
      if (arguments.length < 3) {
        return createWrapper(func, BIND_FLAG, null, thisArg);
      }
      if (func) {
        var arity = func[expando] ? func[expando][2] : func.length,
            partialArgs = slice(arguments, 2);

        arity -= partialArgs.length;
      }
      return createWrapper(func, BIND_FLAG | PARTIAL_FLAG, arity, thisArg, partialArgs);
    }
Creates a function that, when called, invokes `func` with the `this`
binding of `thisArg` and prepends any additional `bind` arguments to those
provided to the bound function.

Note: Unlike native `Function#bind` this method does not set the `length`
property of bound functions.

@static
@memberOf _
@category Functions
@param {Function} func The function to bind.
@param {*} [thisArg] The `this` binding of `func`.
@param {...*} [args] Arguments to be partially applied.
@returns {Function} Returns the new bound function.
@example

var func = function(greeting) {
  return greeting + ' ' + this.name;
};

func = _.bind(func, { 'name': 'fred' }, 'hi');
func();
// => 'hi fred'