[BUG] Using esbuild to generate an ESM .mjs bundle

[Mystogab]

when trying to run this library as an ESM, for instance using esbuild to generate a .mjs file. It fails tu run on AWS lambda with this error:

2025-11-10T21:22:36.250Z	undefined	ERROR	Uncaught Exception 	
{
    "errorType": "Error",
    "errorMessage": "Dynamic require of \"querystring\" is not supported",
    "stack": [
        "Error: Dynamic require of \"querystring\" is not supported",
        "    at file:///var/task/api.mjs:1:388",
        "    at <anonymous> (/var/node_modules/lambda-api/lib/request.js:8:12)",
        "    at file:///var/task/api.mjs:1:499",
        "    at <anonymous> (/var/node_modules/lambda-api/index.js:8:17)",
        "    at file:///var/task/api.mjs:1:499",
        "    at <anonymous> (/var/apps/api/shells/input/api-gateway-shell.ts:3:23)",
        "    at ModuleJob.run (node:internal/modules/esm/module_job:343:25)",
        "    at async onImport.tracePromise.__proto__ (node:internal/modules/esm/loader:647:26)",
        "    at async _tryAwaitImport (file:///var/runtime/index.mjs:1098:16)",
        "    at async _tryRequire (file:///var/runtime/index.mjs:1156:86)"
    ]
}

By adding this

banner: {
    js: "import { createRequire } from 'module'; const require = createRequire(import.meta.url);",
  },

to your esbuild build configuration, or manually adding that line at the top of the output bundled file it works on AWS Lambda using ESM and an MJS entrypoint file.

[Mystogab]

Note:
I tried replacing the querystring import for this:

function parseQS(bodyString) {
  // ... (implementation remains the same as previous response) ...
  if (typeof bodyString !== 'string') {
    return {};
  }
  
  // Pass the raw body string directly to the constructor:
  const params = new URLSearchParams(bodyString); 
  const result = {};

  for (const [key, value] of params.entries()) {
    if (Object.prototype.hasOwnProperty.call(result, key)) {
      if (Array.isArray(result[key])) {
        result[key].push(value);
      } else {
        result[key] = [result[key], value];
      }
    } else {
      result[key] = value;
    }
  }

  return result;
}

but then I got the error with 'crypto' so Im sure it needs to be addressed diffrently but didn't have time to figure it out

[naorpeled]

Hey @Mystogab
Thanks for opening this issue, I will try to get to this asap.
In the meantime I'll try to let Copilot try and resolve this 🙏

[Mystogab]

Hey @Mystogab Thanks for opening this issue, I will try to get to this asap. In the meantime I'll try to let Copilot try and resolve this 🙏

Thanks for receiving my feedback! I was just about to suggest to add an index.mjs plus package.json addition of that entrypoint as possible solution, seem like copilot proposed a suitable solution, I will test it during this week.

Happy to do my bit in this awesome library!

[Mystogab]

Hey there @naorpeled
I've been testing the project and noticed that it currently doesn't seem to work with the Copilot approach.

I've explored a potential solution that involves some deeper changes to the codebase. It might be possible to use esbuild to generate both CJS and ESM bundles. Shipping both would ensure compatibility and allow for tree-shaking when used with modern bundlers (like esbuild, Parcel, or Bun).

However, this would require migrating the codebase from require() statements to import/export syntax.

I'm happy to take this on myself! I can prepare a Pull Request that includes these changes, along with a prepublishOnly script to ensure the packages are correctly generated during the publishing process.

I wanted to get your thoughts on this approach first. What do you think?

[naorpeled]

Hey there @naorpeled
I've been testing the project and noticed that it currently doesn't seem to work with the Copilot approach.

I've explored a potential solution that involves some deeper changes to the codebase. It might be possible to use esbuild to generate both CJS and ESM bundles. Shipping both would ensure compatibility and allow for tree-shaking when used with modern bundlers (like esbuild, Parcel, or Bun).

However, this would require migrating the codebase from require() statements to import/export syntax.

I'm happy to take this on myself! I can prepare a Pull Request that includes these changes, along with a prepublishOnly script to ensure the packages are correctly generated during the publishing process.

I wanted to get your thoughts on this approach first. What do you think?

Sounds good to me!
Feel free to ping me if you need anything, and thank you for your help, it's much appreciated!