Now if you are planning to learn Ext JS, you should say goodbye to using plain JavaScript. JavaScript is a great, excellent language, but as web applications get larger and larger, our code becomes increasingly difficult to maintain, which is very difficult and time-consuming.

Ordinary JavaScript is very flexible, which has many advantages. At the same time, it will also bring many problems. As your application becomes larger and larger, more and more people will participate. Ordinary JavaScript can be written by 10 people. There will be 10 different styles. There are often some codes that only the person who wrote the code knows why they were written that way. If this person is no longer responsible for this function, it will become a trap for future generations. Therefore, constraints and specifications on the code are very necessary. This is why I have always liked ExtJS. ExtJS writes code just like Java, very rigorous and very object-oriented. The disadvantage is that it is relatively heavyweight among front-end JS libraries and has a relatively steep learning curve.

When it comes to JavaScript frameworks, there are client-side JavaScript frameworks as well as server-side JavaScript frameworks. Ext JS is a client-side JavaScript framework.