AS2 conformed partially to ECMAScript 4 and I believe AS3 was a superset of ECMAScript 4. They had a lot of features that current developers complain about vanilla JS even today such as compile-time and run-time type-checking. Flash/AS had its creative uses, I wrote a client library for a SAAS medical records applications for doctors that worked around some of the limitations on filesizes for multipart forms in 2012 that allowed me to chunk the upload of multi-megapixel webcam images so doctors could take pictures and attach them to patient records. A fun chance to solve a vexing problem, at least at that time.