When should I use call() vs invoking the function directly?

Question

I\'ve got a JavaScript application that uses a lot of callbacks. A typical function will take a callback, and wrap it with another callback.

Namespace.foo = func         


        

Answer 1

A good example is when implementing a function that needs a callback. When writing OO code, you want to allow the caller to specify the context that a callback will be called.

function validateFormAjax(form, callback, context) {
  // Using jQuery for simplicity
  $.ajax({
    url: '/validateForm.php',
    data: getFormData(form),
    success: function(data) {
      callback.call(context, data);
    }
  });
}

Note that my example could just be implemented by passing the context parameter to the $.ajax call, but that wouldn't show you much about using call