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How to have better NPM Scripts

raulfdm profile image Raul Melo Originally published at raulmelo.dev ・5 min read

As a JavaScript developer (no matter back or front-end), we often rely upon npm scripts to automate common tasks like starting a server, building a project, and even performing tasks before or after certain scripts like postbuild, prebuild, etc.

When those commands are simple like node index.js, having them a single line in our package.json isn't a problem at all. The real problem starts when we need an extensive command, adding environment variables, and concatenating commands:

(Example extracted from Material UI package.json)

{
    "scripts": {
      "proptypes": "cross-env BABEL_ENV=development babel-node --extensions \".tsx,.ts,.js\" ./scripts/generateProptypes.ts",
      "deduplicate": "node scripts/deduplicate.js",
      "benchmark:browser": "yarn workspace benchmark browser",
      "build:codesandbox": "lerna run --parallel --scope \"@material-ui/*\" build",
      "release:version": "lerna version --exact --no-changelog --no-push --no-git-tag-version",
      "release:build": "lerna run --parallel --scope \"@material-ui/*\" build",
      "release:changelog": "node scripts/releaseChangelog",
      "release:publish": "lerna publish from-package --dist-tag next --contents build",
      "release:publish:dry-run": "lerna publish from-package --dist-tag next --contents build --registry=\"http://localhost:4873/\"",
      "release:tag": "node scripts/releaseTag",
      "docs:api": "rimraf ./docs/pages/api-docs && yarn docs:api:build",
      "docs:api:build": "cross-env BABEL_ENV=development __NEXT_EXPORT_TRAILING_SLASH=true babel-node --extensions \".tsx,.ts,.js\" ./docs/scripts/buildApi.ts  ./docs/pages/api-docs ./packages/material-ui-unstyled/src ./packages/material-ui/src ./packages/material-ui-lab/src --apiPagesManifestPath ./docs/src/pagesApi.js",
      "docs:build": "yarn workspace docs build",
      "docs:build-sw": "yarn workspace docs build-sw",
      "docs:build-color-preview": "babel-node scripts/buildColorTypes",
      "docs:deploy": "yarn workspace docs deploy",
      "docs:dev": "yarn workspace docs dev",
      "docs:export": "yarn workspace docs export",
      "docs:icons": "yarn workspace docs icons",
      "docs:size-why": "cross-env DOCS_STATS_ENABLED=true yarn docs:build",
      "docs:start": "yarn workspace docs start",
      //.....
    }
}
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But what if I told you could have those commands extracted into a separate file and having a scripts config like this:

{
    "scripts": {
      "proptypes": "scripty",
      "deduplicate": "scripty",
      "benchmark:browser": "scripty",
      "build:codesandbox": "scripty",
      "release:version": "scripty",
      "release:build": "scripty",
      "release:changelog": "scripty",
      "release:publish": "scripty",
      "release:publish:dry-run": "scripty",
      "release:tag": "scripty",
      "docs:api": "scripty",
      "docs:api:build": "scripty",
      "docs:build": "scripty",
      "docs:build-sw": "scripty",
      "docs:build-color-preview": "scripty",
      "docs:deploy": "scripty",
      "docs:dev": "scripty",
      "docs:export": "scripty",
      "docs:icons": "scripty",
      "docs:size-why": "scripty",
      "docs:start": "scripty",
    }
   //.....
}
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Scripty

Scripty is an npm package that enables us the ability to have executable files to run npm scripts.

The whole idea is to treat these giant script lines we have as code and keep our package.json clean and simple.

Let's say we have this:

{
  "scripts": {
    "lint": "eslint . --cache --report-unused-disable-directives --ext .js,.ts,.tsx --max-warnings 0"
  }
}

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Using scripty it'll look like this:

{
  "scripts": {
    "lint": "scripty"
  }
}
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The magic behind

Of course, the command we just removed needs to be somewhere. To make it simple as that, scripty does a pairing of <npm-script-nam>:<executable-file-name>.

In other words, if we have an npm script called lint, we need an executable file called lint, lint.sh, or lint.js.

The default folder is always, at the root level, a folder called scripts. So, to solve the previous migration, we would create a file called lint.sh under the scripts folder, like this:

#!/usr/bin/env bash

yarn eslint . --cache --report-unused-disable-directives --ext .js,.ts,.tsx --max-warnings 0
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Executable Bash or .JS

Scripty can handle only handle executable bash or JavaScript executables.

To have one of those, the file needs to:

  1. having the shebang at the top of the file (e.g. #!/bin/bash or #!/bin/node;
  2. having permission to execute (while ls -la, it needs to have x flag);

Quick tip, if you're in a UNIX environment, you can quickly give this permission by running the command chmod u+x <file-path>

Also, file extensions are not necessary. You can write a test.sh, test.js or only test. What will define the syntax highlight and the execution will be one of the shebang instructions I've mentioned before.

#!/bin/node

const fs = require('fs');

fs.copyFileSync('static/base.css', 'dist/base.css');
// ...
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#!/usr/bin/env bash

NODE_ENV=production

yarn nest build
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For JS executable, keep in mind that it'll be executed by node and you can't use invalid js-node (e.g. import) syntax.

Batching

Another requirement we often have is running a bunch of scripts related. Let's say we have a lot of test script and we want to run all of them, like test:*:

{
  "scripts": {
    "test:unit": "jest",
    "test:e2e": "cypress run --ci",
    "test": "npm-run-all test:*",
  }
}
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With scripty, we can create a subfolder called test and declare those 2 types of tests there:

.
├── package.json
├── scripts
│   └── test
│       ├── e2e
│       └── unit
└── yarn.lock
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By having those files with those instructions, you can change your package.json to be:

{
  "scripts": {
    "test:unit": "scripty",
    "test:e2e": "scripty",
    "test": "scripty",
  }
}
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Note that only the test script will be sufficient for this case. We'll only keep test:unit and test:e2e in case we want to run one of these commands isolated.

When you run test, scripty will understand you have a folder called test with a lot of scripts and it'll run all of them.

Keep in mind that this is a concurrency call and you should not rely on the execution order.

Controlling the batching sequence

If you need them being executed in a certain order, with the same package.json as before, all you need to do is, in our scripts/test folder, creates a script called index witch will be responsible for executing the other scripts in the sequence we want to:

.
├── package.json
├── scripts
│   └── test
│       ├── index
│       ├── integration
│       └── unit
└── yarn.lock
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#!/bin/bash

scripts/test/unit
scripts/test/integration
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Keep in mind that the current working directory (CWD) will be always where it's being executed, in that case, our root folder.

Parallel watch

Another common scenario is when we have certain scripts we need to run which will stay in watch mode, in other words, lock a section and keep listening for file changes so it can perform something.

{
  "scripts": {
    "watch:css": "sass src/scss/main.scss public/css/main.css -s compressed",
    "watch:js": "webpack --config webpack.config.js --watch --mode=development",
  }
}
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A way of booting both commands would be opening two tabs and running each command in a tab. But that's tedious. What if we could somehow have a single terminal tab and run all watch at the same time?

To do that using scripty all we have to do is to create a folder called watch inside scripts, pretty much as we did before for test

.
├── package.json
├── scripts
│   └── watch
│       ├── css
│       └── js
└── yarn.lock
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But instead of only passing scripty word to our npm script, we have to specify an environment variable called SCRIPTY_PARALELL with true:

{
  "scripts": {
    "watch": "SCRIPTY_PARALLEL=true scripty"
  }
}
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Now both will keep running.

Caveats

The biggest caveat here is for windows users.

If you're one of them or you maintain a project which can be run in a Windows machine, you'll need some special treatment for that and I suggest you take a look at their docs with those instructions.

Conclusion

Scripty allows us to treat or npm scripts as code, having a file containing all instructions to execute some tasks.

It also eases the ability to roll back an incorrect script instruction and provides a great and isolated git history.

So be creative.

References

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