Is it possible for parameters to still be filled even when they start off empty

Currently, I am enrolled in a javascript course and struggling to comprehend how the parameter in my example below is populated with the "correct stuff" without actually calling the function with a corresponding element?

  success: function(result) {
    $('myElement').html(result);
  }

I suspect there might be some default behavior at play that I overlooked. Can anyone shed some light on this for me? Any help would be greatly appreciated. /Kristofer Guldvarg

Answer №1

Let's break down how jQuery is explained (for those who are very curious, you can find the actual AJAX implementation here);

var jQuery = {
    ajax: function (obj) {
        var xhr = new XMLHttpRequest();

        xhr.onreadystatechange = function () {
            if (this.readyState === 4 && this.status === 200) {
                obj.success(this.textContent);
            }
        }

        xhr.open(obj.url, 'GET', false);
        xhr.send(null);
    }
};

So when you execute;

jQuery.ajax({
    url: '/foo.php',
    success: function (response) {
        $('myElement').html(result);
    }
});

.. jQuery has the ability to invoke the success function by using obj.success, and then transfer whatever data it needs (like in this case this.textContent).

You're not directly invoking the function; instead, you are defining a function and passing it on to be used elsewhere, allowing others to trigger it later on and pass along necessary information.

Answer №2

It appears to be a callback situation here. Another function is expected to trigger it at some stage and send over the outcome.

What's happening is you're invoking a function that requires a win function. Essentially, you are instructing it to say "Hey, once you finish with that task, make sure to call this win function I've provided and pass on the result you generated."

Answer №3

This is an example of a callback function that has been incorporated as a closure.

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