Check if there is a “node_modules” directory
If not, enter the command first:
npm install
Next step.
Open the package.json file and add the following
"scripts": {
"start": "node dev-server.js 8080"
},
Add node to the start file name you want to run (no need to add a directory in the root directory, other directories need a directory, the root directory is ./) and the port number
*Notice! *The last comma is unnecessary if added to the end of the file.
After the modification is complete, use npm start again.