While "$ npm run watch" is running, if a file in a directory is modified, then run a custom script

I have the following dummy Laravel 5.5 + React project:

$ git clone https://github.com/tlg-265/laravel-5.5-react.com
$ cd laravel-5.5-react.com
$ npm i
$ npm run watch

My goal is: while: $ npm run watch is running, whenever some of the files: /template/template-XX.json is modified, the script /template/listener.js be executed.

When that happens, the variable: template (inside: listener.js) should get the name of that modified file (JSON file above), for example: template-02.json.

Here is the content of file /template/listener.js:

var template = '###TBD###';
console.log(`The template: ${template} was modified.`);

Probably one way to achieve that is to configure the file: package.json accordingly. This is the content of file: package.json:

  "private": true,
  "scripts": {
    "dev": "npm run development",
    "development": "cross-env NODE_ENV=development node_modules/webpack/bin/webpack.js --progress --hide-modules --config=node_modules/laravel-mix/setup/webpack.config.js",
    "watch": "cross-env NODE_ENV=development node_modules/webpack/bin/webpack.js --watch --progress --hide-modules --config=node_modules/laravel-mix/setup/webpack.config.js",
    "watch-poll": "npm run watch -- --watch-poll",
    "hot": "cross-env NODE_ENV=development node_modules/webpack-dev-server/bin/webpack-dev-server.js --inline --hot --config=node_modules/laravel-mix/setup/webpack.config.js",
    "prod": "npm run production",
    "production": "cross-env NODE_ENV=production node_modules/webpack/bin/webpack.js --no-progress --hide-modules --config=node_modules/laravel-mix/setup/webpack.config.js"
  "devDependencies": {
    "axios": "^0.17",
    "babel-preset-react": "^6.23.0",
    "bootstrap-sass": "^3.3.7",
    "cross-env": "^5.1",
    "jquery": "^3.2",
    "laravel-mix": "^1.0",
    "less": "^3.11.1",
    "less-loader": "^5.0.0",
    "lodash": "^4.17.4",
    "react": "^15.4.2",
    "react-dom": "^15.4.2"

Just in case, this is a preview of the file structure:

enter image description here

Any idea on how to achieve that?