Do I need to run “npm run build” every time I made changes?

So finally, I have found my solution. When you want to re-run “npm run build” every time a file changes. You need to install watch via npm. It checks all the files inside a directory and when you change something or on-save, it will re-run all the scripts inside package.json. So steps –

1. Install watch by

   npm install watch
   

2. When watch is installed, add

   "watch": "watch 'npm run build' ./directory-you-want-to-track"
   

3. Run

   npm run watch