Laravel Mix - 包含/加载JavaScript文件序列问题

Question

I am new to Laravel mix and I am trying to port a current app to Laravel. My issue is when I try to access a function that is in a different Javascript file which is then placed into app.js using Laravel Mix, I have played around with the order of the files which did not make a difference. The only thing that seems to work is have the function in the same file that is calling it, which is what mix should do. I would like to keep them in a separate file so that I can manage them easier in Laravel and custom-queries.js is to be used in multiple apps.

app.js

require('./bootstrap');
require('./apps/custom-queries');
require('./apps/barcode-gen/user-input');

webpack.mix.js

mix.js('resources/assets/js/app.js', './public/js')
   .sass('resources/assets/sass/app.scss', './public/css');

custom-queries.js

function BarcodesPOSearch(poNumber) {
  console.log('test');
}

user-input.js

$(document).on('click', '#search-by-po-inputs button', function() {
   BarcodesPOSearch($poNumber);
});

Console Error

app.js:32946 Uncaught ReferenceError: BarcodesPOSearch is not defined
    at HTMLButtonElement.<anonymous> (app.js:32946)
    at HTMLDocument.dispatch (app.js:23180)
    at HTMLDocument.elemData.handle (app.js:22988)