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Cover image for Adding URL Search Parameters to Imports!
Lioness100
Lioness100

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Adding URL Search Parameters to Imports!

#typescript #javascript #tutorial #node

Here's an interesting bit of knowledge: did you know that you can create and interpret relative file URLs like... actual URLs?

All content covered in this post will only work with ESM

Now, it might be hard to find a practical use for this, but it is undoubtedly very cool 😎. Enough talk; let's look at some code.



// In your first file:
import './example.js?abc=123';
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// In your second file, example.js:
const url = new URL(import.meta.url);
const searchParam = url.searchParams.get('abc');

console.log(searchParam); // → '123'
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Here, import.meta.url is used to display the full URL used to import the module. In this case, for example, it might be:



file:///C:/Some/Folder/Path/example.js?abc=123
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From here, we can create an instance of a URL, which will make it super easy to parse search parameters.

How could this be used?

I have no idea 😂! Maybe it could be used as a shortcut for very primitive module configuration? For example, using the very popular utility package dotenv.

GitHub logo motdotla / dotenv

Loads environment variables from .env for nodejs projects.

🎉 announcing dotenvx. run anywhere, multi-environment, encrypted envs

 

dotenv NPM version

dotenv

Dotenv is a zero-dependency module that loads environment variables from a .env file into process.env. Storing configuration in the environment separate from code is based on The Twelve-Factor App methodology.

js-standard-style LICENSE codecov

🌱 Install

# install locally (recommended)
npm install dotenv --save
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Or installing with yarn? yarn add dotenv

🏗️ Usage

how to use dotenv video tutorial youtube/@dotenvorg

Create a .env file in the root of your project (if using a…

View on GitHub

Instead of:



import dotenv from 'dotenv';
dotenv.config({ debug: true });
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You could do this! 🦄



import 'dotenv/config?debug=true';
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I'd love to know your thoughts 😆

Top comments (6)

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servernoj profile image
servernoj • • Edited

Does anybody know how to use this trick with Typescript? Say, I have a TS project with "type": "module" in package.json and "module" set to "esnext" in tsconfig.json. Then, I have 2 TS files in the same directory, e.g. a.ts and b.ts with a line in b.ts reading:

import {...} from './a.js'
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and it works fine after compilation with tsc (please notice the use of a.js instead of a in the import statrement -- this is a requirement for imports of local ESM modules)

But... when I replace import statement to

import {...} from './a.js?q=hello'
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then tsc throws error that it cannot find module.

The only solution that I know is to suppress TS error checking by adding @ts-ignore like that:

// @ts-ignore
import {...} from './a.js?q=hello'
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gabrielrurbina profile image
Gabriel Urbina •

There is limited support for this, add this into your tsconfig.json,

{
    "compilerOptions": {
        "paths": {
            "./somedir/*?q=hello": [
                "./somedir/*"
            ]
        }
    }
}
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Have a look at path-mapping

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abc_wendsss profile image
Wendy Wong •

Great article by Lioness100 and thanks @servernoj for asking a thoughtful question and sharing with the DEV community 🙂

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kopseng profile image
Carl-Erik Kopseng •

Here's an actual usage for you: cache busting the browser's cached resolution of module imports after it has failed. You see, browsers cache the initial loading of a module, including the failure state, so that the runtime does not have to download the same module multiple times. Unfortunately, that means an intermittent network error in your SPA will make it fail consistently.

That's why I published this library to catch those errors and retry by appending a cache busting query parameter to the module path.

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prantlf profile image
Ferdinand Prantl • • Edited

I use it in my test harness to create a named test suite by a single import line. Instead of the usual importing index.min.mjs and calling the test suite factory:

import tehanu from './node_modules/tehanu/dist/index.min.mjs'

const test = tehanu('sum')
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I can import suite.min.mjs which recognises the URL parameter name, creates a test suite with the name and exports it:

import test from './node_modules/tehanu/dist/suite.min.mjs?name=sum'
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It's a pity that this works only in browsers. Node.js doesn't separate the URL parameters from the file path, which leads to an invalid script path, if they are attached:

❯ node 'lib/index.mjs'
no suites

❯ node 'lib/index.mjs?test'
node:internal/modules/cjs/loader:936
  throw err;
  ^
Error: Cannot find module '/.../tehanu/packages/teru/lib/index.mjs?test'
    at Function.Module._resolveFilename (node:internal/modules/cjs/loader:933:15)
    at Function.Module._load (node:internal/modules/cjs/loader:778:27)
    at Function.executeUserEntryPoint [as runMain] (node:internal/modules/run_main:77:12)
    at node:internal/main/run_main_module:17:47 {
  code: 'MODULE_NOT_FOUND',
  requireStack: []
}
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This has probably a consequence that the URL parameters can't be used in subpackages either. If a library exposes a subpackage suite, for example:

{
  "exports": {
    ".": {
      "require": "./lib/index.cjs",
      "import": "./lib/index.mjs"
    },
    "./suite": "./lib/suite.mjs"
  }
}
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it has to be used as-is:

import test from 'tehanu/suite'
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instead of the desired:

import test from 'tehanu/suite?name=sum'
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which fails:

❯ node lib/index.mjs test/index.mjs
node:internal/errors:465
    ErrorCaptureStackTrace(err);
    ^
Error [ERR_PACKAGE_PATH_NOT_EXPORTED]: Package subpath './suite?name=sum' is not defined by "exports" in /.../tehanu/packages/teru/node_modules/tehanu/package.json imported from /.../tehanu/packages/teru/test/index.mjs
    at new NodeError (node:internal/errors:372:5)
    at throwExportsNotFound (node:internal/modules/esm/resolve:472:9)
    at packageExportsResolve (node:internal/modules/esm/resolve:753:3)
    at packageResolve (node:internal/modules/esm/resolve:935:14)
    at moduleResolve (node:internal/modules/esm/resolve:1003:20)
    at defaultResolve (node:internal/modules/esm/resolve:1218:11)
    at ESMLoader.resolve (node:internal/modules/esm/loader:580:30)
    at ESMLoader.getModuleJob (node:internal/modules/esm/loader:294:18)
    at ModuleWrap.<anonymous> (node:internal/modules/esm/module_job:80:40)
    at link (node:internal/modules/esm/module_job:78:36) {
  code: 'ERR_PACKAGE_PATH_NOT_EXPORTED'
}
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Related:

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lioness100 profile image
Lioness100 •

WOW! I never thought of that use case, and your findings are really interesting! Thank you so much!! ♥️♥️

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