bundle-build.js

const webpack = require('webpack');
const globber = require('glob');
const { readFile, writeFile } = require('fs');

const buildPattern = process.argv[2];

const glob = (globPattern) => new Promise((r) => {
 globber(globPattern, (_, s) => r(s));
});

glob(buildPattern).then((files) => {
 const bundle = function bundle(i = 0) {
  if (i < files.length) {
   const entryFile = files[i];
   const outputFile = entryFile.replace('user.js', 'bundle.user.js');
   const distFile = `./dist${outputFile.slice(1)}`;
   const metaFile = distFile.replace('user.js', 'meta.js');
   console.log(entryFile);
   console.log(outputFile);
   console.log(distFile);
   webpack(
    {
     mode: 'production',
     entry: entryFile,
     output: {
      filename: outputFile,
     },
    },
    (err, stats) => {
     if (err) {
      console.error(err.stack || err);
      if (err.details) {
       console.error(err.details);
      }

      return;
     }

     const info = stats.toJson();

     if (stats.hasErrors()) {
      console.error(info.errors);
     }

     if (stats.hasWarnings()) {
      console.warn(info.warnings);
     }

     const delimiter = '==/UserScript==\n';
     readFile(entryFile, (readEntryFileErr, result) => {
      if (readEntryFileErr) {
       console.error(readEntryFileErr);
      } else if (result.toString().includes(delimiter)) {
       const userscriptHeader = result.toString().split(delimiter)[0] + delimiter;
       readFile(distFile, (readDistFileErr, distFileContent) => {
        if (readDistFileErr) {
         console.error(readDistFileErr);
        } else {
         const bundleWithHeader = userscriptHeader + distFileContent.toString();
         writeFile(distFile, bundleWithHeader, (writeDistFileErr) => {
          if (writeDistFileErr) {
           console.error(writeDistFileErr);
          } else {
           writeFile(metaFile, userscriptHeader, (writeMetaFileErr) => {
            if (writeMetaFileErr) {
             console.error(writeMetaFileErr);
            } else {
             bundle(i + 1);
            }
           });
          }
         });
        }
       });
      } else {
       console.log('no userscript header');
       bundle(i + 1);
      }
     });
    },
   );
  }
 };
 bundle();
});