Is it possible to load asynchronous JS and then execute functions?

Question

Is it possible to load asynchronous JS and then execute functions?

Is there a way to make my script behave like the Google Analytics JavaScript snippet? Here is an example of what I have:

(function(d, t) {
    var g = d.createElement(t),
        s = d.getElementsByTagName(t)[0];
    g.src = 'myjs.js';
    s.parentNode.insertBefore(g, s);
}(document, 'script'));

In this script, a class is defined. But when I try to call it like this:

var newClass = new myclass('myparam');

I receive a 'not defined' error. However, if I wait and call it again in the console, the error no longer occurs. It seems like the script has not fully loaded yet, which is why the class does not exist.

On the other hand, you can call Google Analytics functions directly after importing, as shown here:

(function(i,s,o,g,r,a,m){i['GoogleAnalyticsObject']=r;i[r]=i[r]||function(){
(i[r].q=i[r].q||[]).push(arguments)},i[r].l=1*new Date();a=s.createElement(o),
m=s.getElementsByTagName(o)[0];a.async=1;a.src=g;m.parentNode.insertBefore(a,m)
})(window,document,'script','//www.google-analytics.com/analytics.js','ga');

ga('create', '[userid]', '[website]');

How can I achieve similar behavior with my own script?

javascript ajax import

Answer 1

Answer №1

The purpose of the GA code is to immediately create an object using inline code that stores calls in an array until the GA script is loaded and then consumes the array. This process cannot be replicated with the constructor function shown due to its reliance on a return value.

Let's delve into the specifics of what the GA code accomplishes:

(function (i, s, o, g, r, a, m) {
    // Define 'ga' as the GoogleAnalyticsObject property on the window
    i['GoogleAnalyticsObject'] = r;

    // Create or retrieve the 'ga' function. If one exists, use it; if not, create a new function.
    i[r] = i[r] || function () {
        // Initialize an array if none exist, then push current arguments
        (i[r].q = i[r].q || []).push(arguments)
    }, i[r].l = 1 * new Date(); // Capture timestamp when code runs

    // Load GA script asynchronously after setup
    a = s.createElement(o),
    m = s.getElementsByTagName(o)[0];
    a.async = 1;
    a.src = g;
    m.parentNode.insertBefore(a, m)
})(window, document, 'script', '//www.google-analytics.com/analytics.js', 'ga');

Answer 2

The purpose of the GA code is to immediately create an object using inline code that stores calls in an array until the GA script is loaded and then consumes the array. This process cannot be replicated with the constructor function shown due to its reliance on a return value.

Let's delve into the specifics of what the GA code accomplishes:

(function (i, s, o, g, r, a, m) {
    // Define 'ga' as the GoogleAnalyticsObject property on the window
    i['GoogleAnalyticsObject'] = r;

    // Create or retrieve the 'ga' function. If one exists, use it; if not, create a new function.
    i[r] = i[r] || function () {
        // Initialize an array if none exist, then push current arguments
        (i[r].q = i[r].q || []).push(arguments)
    }, i[r].l = 1 * new Date(); // Capture timestamp when code runs

    // Load GA script asynchronously after setup
    a = s.createElement(o),
    m = s.getElementsByTagName(o)[0];
    a.async = 1;
    a.src = g;
    m.parentNode.insertBefore(a, m)
})(window, document, 'script', '//www.google-analytics.com/analytics.js', 'ga');

Is it possible to load asynchronous JS and then execute functions?

Answer №1

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