An example javascript api-based `esbuild` build script with a watch and automatic post-build bash script execution.

build.js

// As discussed in https://github.com/evanw/esbuild/issues/1688

require('esbuild').build({
  entryPoints: ['./briefings/frontend/src/briefings.ts'],
  outfile: './briefings/frontend/build/briefings-fe.js',
  bundle: true,
  minify: true,
  target: 'es2017',
  color: true,
  watch: {
    onRebuild(error, result) {
      const verboseOutput = false;

      console.log(`File change at ${new Date()}`);
      console.log('Rebuilding...');

      if (error) console.error('Watch build failed:', error);
      else if (verboseOutput) console.log('Build complete', result);
      else console.log('Build complete.');

      const util = require('util');
      const exec = util.promisify(require('child_process').exec);

      async function runPostBuildScript() {
        try {
          console.log('Running post-build script...');
          const { stdout, stderr } = await exec('./postbuild.sh');
          if (stdout !== '') console.log(stdout);
          if (stderr !== '') console.log(`Errors :, ${stderr}`);
        } catch (e) {
          console.error(e); // should contain code (exit code) and signal (that caused the termination).
        }
      }

      runPostBuildScript().then(() => {
        console.log('Post-build script complete.\n');
      });
    },
  },
}).then(() => {
  console.log('esbuild is watching for changes. (ctrl-c to quit)\n');
  // Call "stop" on the result when you're done
  // result.stop();
});