Production JS code in multiple files

I want to create my JavaScript code in a few files, e.g. product.js, ajax.js, etc… (it means \assets\scripts\*.js).
And finally I want to gulp combine all my JS files from \assets\scripts\ folder and Bootstrap JS files and create one file main.js.

On this moment gulp ignore JS files from \assets\scripts\ folder except main.js from this folder.

How should it look code in gulpfile.js to combine all JS files from \assets\scripts\
to one main.js file in \dist\scripts\?

What have you tried so far?

I found solution. I edited file /assets/manifest.json.
I add here path to all my JS files:

   "dependencies": {
   "main.js": {
      "files": [
         "scripts/file-1.js", // changed by me
         "scripts/file-2.js", // changed by me
      "main": true

…and it works fine.

Sorry for the problem.