What is the difference between yarn run and npm start?

Yarn run and npm start are both commonly used commands in modern frontend development for launching applications. However, there are some subtle differences between them:

1. Command Line Tools:

   • npm start is part of the npm package manager, which serves as Node.js's default package manager and has been widely used since Node.js was introduced.
   • yarn run is a command of the Yarn package manager, developed by Facebook to address certain limitations of npm, such as performance and security issues, and has been widely adopted since 2016.

2. Performance:

   • Yarn is generally considered superior to npm in terms of performance. This is because Yarn generates a yarn.lock file during installation, ensuring more accurate and consistent version control for dependencies, while its caching mechanism is also more efficient than npm's.
   • npm has made significant optimizations in recent versions, such as npm 5 introducing package-lock.json, which also strives to maintain consistency in dependency versions.

3. Usage Scenarios:

   • npm start typically points to the start script within the scripts object in the package.json file. This is a convention for the primary method of launching the application.
   • yarn run similarly reads the scripts object in package.json, but it can execute any script defined in the scripts object. For example, running yarn run test will execute the test script.

4. Cross-Platform Compatibility:

   • In cross-platform development, both Yarn and npm support cross-platform operations effectively, reducing platform differences.

5. Example:

   • Suppose in a Node.js project, the scripts section of package.json might look like this:

     json
     {
       "scripts": {
         "start": "node app.js",
         "test": "mocha **/*.test.js"
       }
     }

   • In this case, using npm start and yarn start both execute node app.js to launch the application. However, to run tests, use npm run test and yarn run test respectively.

Although yarn run and npm start are functionally very similar, the main differences lie in the package managers they belong to (Yarn or npm) as well as performance and minor implementation details. Choosing which one typically depends on team preferences or specific project requirements.