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Call a function after external async TweenMax.min.js is loaded

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I would like to call animation functions only after the external GSAP file is loaded. I could place the animation functions after the link to GSAP file like this:

<script src="https://cdnjs.cloudflare.com/ajax/libs/gsap/1.19.0/TweenMax.min.js"></script>
    //my animations

...but I want to load TweenMax.min.js asynchronously and that's the problem:

<script async src="https://cdnjs.cloudflare.com/ajax/libs/gsap/1.19.0/TweenMax.min.js"></script>

I've googled it and found some kind of solution. The idea is to have a global variable created by the the external script and check whether it exists or not. If it exists, then the external JS is loaded. I found the solution here.


So my question is: does TweenMax.min.js create any global variables or objects or whatever I can check the existence of?


Thanks in advance!

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Everything that GSAP uses will be located on this object...


But you could just check if TweenLite exists if that's the only GSAP file you're loading...

if (TweenLite) {
  // Do something


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Hmm... if TweenMax is not loaded then this construction returns an error which look like this:




Here is what I'm doing:

function TweenMaxLoaded() {
    if (TweenMax) { //generates JS error which doesn't allow to execute any other scripts on the page
        console.log ("yes");
        return true;
    } else {
        console.log ("no"); // doesn't show because 
        return false;
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I think that's because you didn't define any scope/context. Have you tried one of these?:

if (window.TweenMax) { ...
if ("TweenMax" in window) { ..
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yes! this works. Thank you!

And sorry for these primitive questions — I'm newbie in JS.


And one more question:

if I place this function inside of JS file like this, it doesn't work again:

<script src="app.js"></script>

It only works from when placed directly in HTML <script> tag.

What's the reason for that?

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Are you getting an error message? Or is it just evaluating to false? I wonder if you're just placing your <script src="app.js"> before you ever load TweenMax. You wouldn't need this kind of "did it load yet" sensing if don't load it async - I'm curious why you're going that route. Also, you'd need to add logic to keep checking - do you have that? The code you're sharing only checks it once. I'd help a LOT if you could share a super simple codepen demo that illustrates the problem you're having so that we can troubleshoot more effectively. Would you mind creating one? See https://greensock.com/forums/topic/9002-read-this-first-how-to-create-a-codepen-demo/ for help doing that. 

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Sorry for the confusion. My last post was the result of my own mistake. But I fixed it already now it works. But I'll explain what I was doing.


I want to load TweenMax asynchronously, so that other JS functions don't have to wait until the GSAP will be loaded. I have construction like this:

<script async src="https://cdnjs.cloudflare.com/ajax/libs/gsap/1.19.0/TweenMax.min.js"></script>
<script async src="app.js"></script>

Inside app.js I will have a lot of different functions. Not only TweenMax animations. This file looks like this now and it works:

var loadtimer;
function TweenMaxLoaded() {
	if (window.TweenMax) {
	} else {
		loadtimer = setInterval(TweenMaxLoaded, 100);

// a lot of other stuff including TweenMax

The error described in the previous post was caused by the animation functions which use TweenMax. I was declaring and executing those functions without waiting for TweenMaxLoaded function. But the TweenMaxLoaded function itself was working properly.


Thanks again! Now even with slow 3G network I can start executing simple functions without waiting for animation scripts  8-)

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