NPM Scripts & Lifecycle Hooks

Intermediatev1.0.0

Master npm scripts for task automation — custom scripts, lifecycle hooks, cross-platform commands, script composition, and replacing Makefiles with package.json scripts.

Content

Overview

NPM scripts are the standard way to automate tasks in JavaScript projects — building, testing, linting, deploying, and more. They replace Makefiles, shell scripts, and task runners with a unified, portable interface.

Why This Matters

-Universal — every JS developer knows npm run
-No extra tools — built into npm, no Gulp/Grunt/Make needed
-Composable — chain scripts with pre/post hooks and operators
-Discoverable — npm run lists all available scripts

Script Composition

json

{
  "scripts": {
    "build": "tsc && npm run build:css",
    "build:css": "tailwindcss -o dist/styles.css --minify",
    "dev": "concurrently \"tsc -w\" \"tailwindcss -w\"",
    "test": "vitest run",
    "test:watch": "vitest",
    "test:coverage": "vitest run --coverage",
    "lint": "eslint src/",
    "lint:fix": "eslint src/ --fix",
    "format": "prettier --write src/",
    "typecheck": "tsc --noEmit",
    "validate": "npm run typecheck && npm run lint && npm run test",
    "clean": "rm -rf dist coverage .next",
    "prepare": "husky"
  }
}

Lifecycle Hooks

json

{
  "scripts": {
    "prebuild": "npm run clean",
    "build": "tsc",
    "postbuild": "echo 'Build complete!'",

    "pretest": "npm run lint",
    "test": "vitest run",

    "prepare": "husky",
    "prepublishOnly": "npm run validate && npm run build"
  }
}

Cross-Platform Commands

json

{
  "scripts": {
    "clean": "rimraf dist coverage",
    "env": "cross-env NODE_ENV=production node server.js",
    "copy": "copyfiles -u 1 src/**/*.json dist/"
  },
  "devDependencies": {
    "rimraf": "^5.0.0",
    "cross-env": "^7.0.0",
    "copyfiles": "^2.4.0"
  }
}

Passing Arguments

bash

# Pass arguments to scripts with --
npm run test -- --watch
npm run lint -- --fix src/components/
npm run build -- --outDir=build

Best Practices

-Use validate script that runs all checks (typecheck + lint + test)
-Use prepare hook for post-install setup (husky, build steps)
-Use prepublishOnly to validate and build before publishing
-Keep scripts short — extract complex logic to shell scripts
-Use cross-platform packages (rimraf, cross-env) for portability
-Add descriptions with comments in a separate scripts section

Common Mistakes

-Using platform-specific commands (rm -rf on Windows fails)
-Forgetting -- when passing arguments to scripts
-Not using prepublishOnly to ensure builds before publish
-Complex multi-line scripts that should be separate files

FAQ

Discussion

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Script Composition

json

{
  "scripts": {
    "build": "tsc && npm run build:css",
    "build:css": "tailwindcss -o dist/styles.css --minify",
    "dev": "concurrently \"tsc -w\" \"tailwindcss -w\"",
    "test": "vitest run",
    "test:watch": "vitest",
    "test:coverage": "vitest run --coverage",
    "lint": "eslint src/",
    "lint:fix": "eslint src/ --fix",
    "format": "prettier --write src/",
    "typecheck": "tsc --noEmit",
    "validate": "npm run typecheck && npm run lint && npm run test",
    "clean": "rm -rf dist coverage .next",
    "prepare": "husky"
  }
}

{ "scripts": { "prebuild": "npm run clean", "build": "tsc", "postbuild": "echo 'Build complete!'", "pretest": "npm run lint", "test": "vitest run", "prepare": "husky", "prepublishOnly": "npm run validate && npm run build" } }

{ "scripts": { "clean": "rimraf dist coverage", "env": "cross-env NODE_ENV=production node server.js", "copy": "copyfiles -u 1 src/**/*.json dist/" }, "devDependencies": { "rimraf": "^5.0.0", "cross-env": "^7.0.0", "copyfiles": "^2.4.0" } }

Best Practices

-Use validate script that runs all checks (typecheck + lint + test)

-Use prepare hook for post-install setup (husky, build steps)

-Use prepublishOnly to validate and build before publishing

-Keep scripts short — extract complex logic to shell scripts

-Use cross-platform packages (rimraf, cross-env) for portability

-Add descriptions with comments in a separate scripts section