Is there a way to customize a package.json file using postinstall?

Question

Is there a way to customize a package.json file using postinstall?

I've developed a package on npm that generates an "scss directory structure" and my goal is to include custom scripts in the package.json file located at the project's root.

MY-PROJECT
├── node_modules
├── scss
└── package.json <--

Currently, all I can do is copy a file named "package.json" to the local directory, potentially overwriting any existing file of the same name.

My intention is not to overwrite existing files, but rather to simply append scripts like "npm run watch," enabling users to jump right into their projects without manually configuring these scripts themselves.

Your assistance is greatly appreciated.

javascript npm package.json npm-scripts post-install

Answer 1

Answer №1

Here is a helpful node.js script for you to use:

post-install.js

const saveFile = require('fs').writeFileSync;

const pkgJsonPath = require.main.paths[0].split('node_modules')[0] + 'package.json';

const json = require(pkgJsonPath);

if (!json.hasOwnProperty('scripts')) {
  json.scripts = {};
}

json.scripts['watch'] = '<some_commands_here>';

saveFile(pkgJsonPath, JSON.stringify(json, null, 2));

package.json

To implement the above script, add the following to the scripts section of your project's package.json file under the postinstall script:

{
  "scripts": {
    "postinstall": "node post-install"
  }
}

_{Note: Make sure that the `post-install.js` script is in the same directory as your `package.json` file.}

Explanation:

The code snippet shown above retrieves the path to the consuming project's package.json using the following line:
```
const pkgJsonPath = require.main.paths[0].split('node_modules')[0] + 'package.json'
```
This logic extracts the pathname at position index 0 from an array returned by require.main.paths, splits it at 'node_modules', and then concatenates 'package.json' to obtain the desired path.
The script then proceeds to parse the package.json file and store the parsed JSON object in the variable json.
If the package.json does not contain a scripts key, one is created with an empty object assignment:
```
if (!json.hasOwnProperty('scripts')) {
  json.scripts = {};
}
```
Following this, a custom npm script can be defined within the script by modifying the placeholder text '<some_commands_here>'. This part of the script allows for flexibility based on individual requirements.
```
json.scripts['watch'] = '<some_commands_here>';
```
Finally, the updated JSON data is converted back into a string format using JSON.stringify(). The modified content is then written back to the original package.json file using fs.writeFileSync().

Answer 2

Here is a helpful node.js script for you to use:

post-install.js

const saveFile = require('fs').writeFileSync;

const pkgJsonPath = require.main.paths[0].split('node_modules')[0] + 'package.json';

const json = require(pkgJsonPath);

if (!json.hasOwnProperty('scripts')) {
  json.scripts = {};
}

json.scripts['watch'] = '<some_commands_here>';

saveFile(pkgJsonPath, JSON.stringify(json, null, 2));

package.json

To implement the above script, add the following to the scripts section of your project's package.json file under the postinstall script:

{
  "scripts": {
    "postinstall": "node post-install"
  }
}

_{Note: Make sure that the `post-install.js` script is in the same directory as your `package.json` file.}

Explanation:

The code snippet shown above retrieves the path to the consuming project's package.json using the following line:
```
const pkgJsonPath = require.main.paths[0].split('node_modules')[0] + 'package.json'
```
This logic extracts the pathname at position index 0 from an array returned by require.main.paths, splits it at 'node_modules', and then concatenates 'package.json' to obtain the desired path.
The script then proceeds to parse the package.json file and store the parsed JSON object in the variable json.
If the package.json does not contain a scripts key, one is created with an empty object assignment:
```
if (!json.hasOwnProperty('scripts')) {
  json.scripts = {};
}
```
Following this, a custom npm script can be defined within the script by modifying the placeholder text '<some_commands_here>'. This part of the script allows for flexibility based on individual requirements.
```
json.scripts['watch'] = '<some_commands_here>';
```
Finally, the updated JSON data is converted back into a string format using JSON.stringify(). The modified content is then written back to the original package.json file using fs.writeFileSync().

Answer 3

Answer №2

If you want to automate tasks in your project, you can create a small script and include commands directly in the scripts section of your package.json.

Example Script:

const data = require("./package.json")
data.scripts["start:dev"] = "npm run dev"
require("fs").writeFileSync(process.cwd() + "/package.json", JSON.stringify(data, null, 2))

Updated package.json:

{
"scripts": {
    "postinstall": "node example-script.js"
  }
}

You can also write a simple inline script as a string and execute it using node -e.

{
"scripts": {
    "postinstall": "node -e 'const data = require(\"./package.json\"); data.scripts[\"start:dev\"] = \"npm run dev\";require(\"fs\").writeFileSync(process.cwd() + \"/package.json\", JSON.stringify(data, null, 2))'"
  },
}

Answer 4

If you want to automate tasks in your project, you can create a small script and include commands directly in the scripts section of your package.json.

Example Script:

const data = require("./package.json")
data.scripts["start:dev"] = "npm run dev"
require("fs").writeFileSync(process.cwd() + "/package.json", JSON.stringify(data, null, 2))

Updated package.json:

{
"scripts": {
    "postinstall": "node example-script.js"
  }
}

You can also write a simple inline script as a string and execute it using node -e.

{
"scripts": {
    "postinstall": "node -e 'const data = require(\"./package.json\"); data.scripts[\"start:dev\"] = \"npm run dev\";require(\"fs\").writeFileSync(process.cwd() + \"/package.json\", JSON.stringify(data, null, 2))'"
  },
}

Answer 5

Answer №3

I encountered a similar issue myself. In case you find yourself needing to make changes to the root package.json file while your module contains a "postinstall" script and is being used as an npm dependency in another project, you will have to navigate through parent directories until you reach a point where no package.json file is found.

const fs = require('fs');
const path = require('path');

let rootPath = '../';
while (!fs.existsSync(path.resolve(rootPath, 'package.json'))){
  rootPath += '../';
}
const pkgJsonPath = path.resolve(rootPath, 'package.json');

Answer 6

I encountered a similar issue myself. In case you find yourself needing to make changes to the root package.json file while your module contains a "postinstall" script and is being used as an npm dependency in another project, you will have to navigate through parent directories until you reach a point where no package.json file is found.

const fs = require('fs');
const path = require('path');

let rootPath = '../';
while (!fs.existsSync(path.resolve(rootPath, 'package.json'))){
  rootPath += '../';
}
const pkgJsonPath = path.resolve(rootPath, 'package.json');

Is there a way to customize a package.json file using postinstall?

Answer №1

Answer №2

Answer №3

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