Why Should You Use Pure JavaScript for UI instead of third party js libraries

There are lot of JavaScript libraries which make the development easier. But when we use a pure JavaScript we understand the core functionality & logic of a JavaScript engine. When we use a new js library we have to learn its own functions, features and their usages and they might also lead to a misconception of JavaScript execution, eg: AngularJS. However, some functionalities like charts/diagrams may not be able to do in a shorter time with pure JavaScript, in such cases we have to rely on third party libs.

When we use third party js libraries which provide ready made ui features we might face some unsolvable issues when customization required for its ui features so if we have a plan for nth level of ui customization then it's always better to use pure JavaScript. Modifying the js library itself is not always safe.