What advantages does using `prestart` offer compared to `&&` in a command within `package.json`?

Question

What advantages does using `prestart` offer compared to `&&` in a command within `package.json`?

I believe the title speaks for itself, but let's dive in:

What advantages does using the pre-script of npm package.json, like prestart, have over simply combining commands with && in the start script?

{
  prestart: "parcel build",
  start "nodemon server.js"
}

compared to

{
 start: "parcel build && nodemon server.js" 
}

Is it more suitable for different platforms?
Can it handle running two asynchronous endless processes, such as two servers (build + api)?

Any other benefits?

Edit: I found a benefit for postInstall. Platforms like Heroku remove devDependency after running npm install, so in the postinstall I can execute the build process before Heroku removes the necessary code.

javascript npm package.json

Answer 1

Answer №1

prestart executes prior to start as the name suggests, leading to a sequential execution of commands in both steps rather than running them in parallel. When using && in start, the commands are executed sequentially but within the same step.

Both approaches yield similar results, but there could be compatibility concerns with && on specific Windows versions.

To perform parallel command execution, you can utilize & within start instead of &&.

Answer 2

prestart executes prior to start as the name suggests, leading to a sequential execution of commands in both steps rather than running them in parallel. When using && in start, the commands are executed sequentially but within the same step.

Both approaches yield similar results, but there could be compatibility concerns with && on specific Windows versions.

To perform parallel command execution, you can utilize & within start instead of &&.

Answer 3

Answer №2

Aside from what has already been mentioned, it is important to highlight that the prestart hook in the package.json file is not compatible with the yarn package manager. Therefore, utilizing && offers a smoother transition between npm and yarn (assuming your shell can interpret &&).

This decision was made to enhance maintainability by steering clear of implicit dependency chains:

We deliberately refrain from supporting arbitrary pre and post hooks for user-defined scripts (like prestart). This practice, inherited from npm, resulted in scripts being implicit rather than explicit, making the execution flow unclear. It also led to unexpected outcomes, such as running both yarn serve and yarn preserve. https://yarnpkg.com/advanced/lifecycle-scripts

Answer 4

Aside from what has already been mentioned, it is important to highlight that the prestart hook in the package.json file is not compatible with the yarn package manager. Therefore, utilizing && offers a smoother transition between npm and yarn (assuming your shell can interpret &&).

This decision was made to enhance maintainability by steering clear of implicit dependency chains:

We deliberately refrain from supporting arbitrary pre and post hooks for user-defined scripts (like prestart). This practice, inherited from npm, resulted in scripts being implicit rather than explicit, making the execution flow unclear. It also led to unexpected outcomes, such as running both yarn serve and yarn preserve. https://yarnpkg.com/advanced/lifecycle-scripts

Answer 5

Answer №3

These techniques are primarily used to enhance code readability and facilitate the separation of logical processes.

In terms of compatibility, npm typically executes all scripts within the local shell environment. This means that on most Linux systems, it will utilize a sh clone, while on Windows it will use cmd. There may be instances where certain shell functionalities like && are not supported. However, it's rare and usually unnecessary to cater to such edge cases, especially since users can easily install bash on any platform where Node.js is present and configure npm accordingly. Personally, I prefer using bash in npm scripts for consistency and document this choice in the README file.

If you need to manage multiple long-running processes, tools like pm2 (https://github.com/Unitech/PM2/) are recommended for production environments. During development, running processes in separate terminals to monitor logs is helpful – consider using supervisor (https://github.com/petruisfan/node-supervisor) to automatically restart processes upon errors or modifications.

Furthermore, creating .sh scripts for maintenance tasks such as deployment and periodic operations is common practice. These scripts can be executed via npm by defining them as named scripts within the scripts section of your project.

Answer 6

These techniques are primarily used to enhance code readability and facilitate the separation of logical processes.

In terms of compatibility, npm typically executes all scripts within the local shell environment. This means that on most Linux systems, it will utilize a sh clone, while on Windows it will use cmd. There may be instances where certain shell functionalities like && are not supported. However, it's rare and usually unnecessary to cater to such edge cases, especially since users can easily install bash on any platform where Node.js is present and configure npm accordingly. Personally, I prefer using bash in npm scripts for consistency and document this choice in the README file.

If you need to manage multiple long-running processes, tools like pm2 (https://github.com/Unitech/PM2/) are recommended for production environments. During development, running processes in separate terminals to monitor logs is helpful – consider using supervisor (https://github.com/petruisfan/node-supervisor) to automatically restart processes upon errors or modifications.

Furthermore, creating .sh scripts for maintenance tasks such as deployment and periodic operations is common practice. These scripts can be executed via npm by defining them as named scripts within the scripts section of your project.

Answer 7

Answer №4

The reason for this is that when you execute a script such as npm install && npm start, both commands are run within the same process in node. Therefore, if one of the commands returns a non-zero exit code (such as an exception), it becomes difficult to pinpoint which command actually failed. By running them as separate scripts using the "pre" keyword, they are executed in separate processes, providing more accurate results.

Answer 8

The reason for this is that when you execute a script such as npm install && npm start, both commands are run within the same process in node. Therefore, if one of the commands returns a non-zero exit code (such as an exception), it becomes difficult to pinpoint which command actually failed. By running them as separate scripts using the "pre" keyword, they are executed in separate processes, providing more accurate results.

What advantages does using `prestart` offer compared to `&&` in a command within `package.json`?

Answer №1

Answer №2

Answer №3

Answer №4

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