How to use ESRI JavaScript API 3.20 and 4.3 in one application ?

[subbaraoP]

We are currently using ESRI JavaScript API 3.20 in our application. We are planning to move ESRI JavaScript API 4.3 but some of the features in 3.20 not available in 4.3 version. We need both features, Can we use two JavaScript API (i.e. 3.20 and 4.3) in one application? Please share an example.

[RobertScheitlin__GISP]

Subbarao,

   You can not use both versions together. You have to choose one or the other. If there are things that you need from 3.x that are not in 4.x then it is just advised to say with 3.x for now.

[ThomasSolow]

I think technically it's possible.  I've seen some references to people doing this here and there, but I don't imagine it's "supported" and I would guess you'd have to have a fairly deep understanding of the dojo loader/various things peripheral to the API in order to get it working.

I'm unsure if people doing this are loading each version separately and keeping them isolated from each other, or if there's a way to use one dojo loader to load modules from both APIs.

[Anonymous User]

No. The references for both the versions are different. Plus mostly all of the features of the version 3.20 is added to 4.3. 

4.3 does have extra and fast features than 3.20.