Ensure to use wisely external libraries, most of the time, you can use a lighter library for a same functionality.
You may be tempted to use one of the 745 000 packages you can find on npm, but you need to choose the best package for your needs. For example, MomentJS is an awesome library but with a lot of methods you may never use, that’s why Day.js was created. It’s just 2kB vs 16.4kB gz for Moment.
Always compare and choose the best and lighter library for your needs. You can also use tools like npm trends to compare NPM package downloads counts or Bundlephobia to know the size of your dependencies.