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How to detect if EasePack was already loaded on the page

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This thread was started before GSAP 3 was released. Some information, especially the syntax, may be out of date for GSAP 3. Please see the GSAP 3 migration guide and release notes for more information about how to update the code to GSAP 3's syntax. 

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What is the most reliable and efficient way to detect if EasePack JS file was already loaded elsewhere on the page and is available (in an effort to prevent loading it again)?


[EDIT: also, detecting if the various plugins were loaded too would be helpful]

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Hey Randall,


Nice to see you in here;)


I'm sure Jack might have a better more efficient approach, but for now I'm thinking you could just test for the existence of an ease that is unique to EasePack and GSAP.


Something like:



console.log("EasePack loaded");
console.log("EasePack not loaded");


if you want to get around any "uncaught exception errors blah blah not defined" this should work too:



try {
var easePackIsLoaded = SlowMo;
easePackIsLoaded = true;
} catch (err) {
var easePackIsLoaded = false;
if (easePackIsLoaded) {
console.log("EasePack is loaded");
} else {
console.log("EasePack is NOT loaded");


I'm sure you know this, but just putting it out there, EasePack is included with TweenMax.js


As for checking the existence of a plugin, I'll let Jack chime in.




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To make things consistent with the Flash version, we put each class at the reverse domain package, so for example the Elastic class is at:




Same with the plugins. For example, you could see if the CSSPlugin was loaded by seeing if this exists:




EasePack is what contains the Elastic class, so you can check for that. And to be clear, "com" is an object at the window level, and "greensock" is an object that's a property of "com", etc. So to avoid errors you could do:


if (com && com.greensock && com.greensock.easing && com.greensock.easing.Elastic) {
   //loaded EasePack


Or create a function that makes it easier like:


//like isLoaded("com.greensock.easing.Elastic")
function isLoaded(class) {
   var parts = class.split("."),
       curPart = window;
   for (var i = 0; i < parts.length; i++) {
       curPart = curPart[parts[i]];
       if (!curPart) {
           return false;
   return true;


Does that help?

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Briliant. Thank you. This is what I was looking for. And I'm always in favor of a wrapper method.


I was previously approaching it from a non-class perspective and simply trying to see if 'something' was undefined or not.


Also, I was making the assumption that once a class was detected that it is also immediately ready for use because it was immediately invoked.

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