JSON (JavaScript Object Notation) is a data format used across applications to share data. The applications can use different languages and they are able to share information using the JSON format.
Node.js and NPM use a JSON file storing configuration details: the package.json file. Besides the package.json file, you may interact with other JSON files located on your local disk. Node.js comes with built-in functionality to read and parse JSON files from your hard drive. Read on for more details!
Node.js Series Overview
- Increase the Memory Limit for Your Process
- Why You Should Add “node” in Your Travis Config
- Create a PDF from HTML with Puppeteer and Handlebars
- Create Your Own Custom Error
- Retrieve a Request’s IP Address in Node.js
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- How to Base64 Encode/Decode a Value in Node.js
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- How to Fix “Uncaught SyntaxError: Cannot use import statement outside a module”
- Fix „Socket Hang Up“ Errors
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- How to Check if a Value is a String in JavaScript or Node.js
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- How to Count Words in a File
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- How to Run an Asynchronous Function in Array.map()
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- Add an Item to the Beginning of an Array in JavaScript or Node.js
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- How to Exit and Stop a for Loop in JavaScript and Node.js
- Split an Array Into Smaller Array Chunks in JavaScript and Node.js
- How to Get an Index in a for…of Loop in JavaScript and Node.js
- How to Exit, Stop, or Break an Array#forEach Loop in JavaScript or Node.js
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- Create and Fill an Array Containing N Items
- Callback and Promise Support in your Node.js Modules
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- Detect if Value Is a Promise in Node.js and JavaScript
- Overview of Promise-Based APIs in Node.js
- Thenables and Creating Your Own Promises
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- Check if a Value is a Number
- How to Merge Objects
- How to Check if an Object is Empty in JavaScript or Node.js
- How to CamelCase Keys of an Object in JavaScript or Node.js
- How to Snake_Case Keys of an Object in JavaScript or Node.js
- How to Destructure a Dynamic Key in JavaScript or Node.js
- How to Get All Keys (Including Symbols) from an Object in JavaScript or Node.js
- How to Delete a Key From an Object in JavaScript or Node.js
- Iterate Through an Object’s Keys and Values in JavaScript or Node.js
- How to Convert URLSearchParams to Object
- Check If a Value Is an Object in JavaScript or Node.js
- Conditionally Add Properties to an Object in JavaScript or Node.js
- How to Lowercase Keys of an Object in JavaScript or Node.js
- Unset an Object Property
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- How to Create an Empty File
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- How to Rename a File
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- Retrieve the Path to the User’s Home Directory
- How to Touch a File
- Read File Content as String
- Check If a Directory Is Empty
- How to Create a Directory (and Parents If Needed)
- Get a File‘s Extension
- Get the Size of a File
- Get a File Name (With or Without Extension)
- Read a JSON File
- Delete a File From Disk
- Check if a Path is a SymLink (Symbolic Link)
- Check if a Path is a Socket
- Check if a Path is a FIFO File (Named Pipe)
- Check if a Path is a File URL
Read and Parse a JSON File From Disk
Node.js provides the fs module to read files from the local hard disk. Use the Fs.readFile to read the content of a given file. Related to a JSON file, you’ll then have the JSON content as a string.
The next step is to parse the JSON string into a JavaScript value. Node.js provides the global JSON class for that. Use the JSON.parse method to convert the JSON string into a JavaScript object
Here’s a code sample reading the local package.json from the hard disk and parsing it into a usable JavaScript object:
const Fs = require('fs/promises')
const json = await Fs.readFile('./package.json')
const package = JSON.parse(json)
package.version
// 3.5.0
You can use the package object like you would use any other JavaScript object.
Read a JSON File Using require()
The CommonJS module loader comes with the require() function. It’s a global function that you typically use to import files within other files. A nice benefit of the require is that it can read and resolve JSON files, too. It loads the JSON file from disk and detects the need to parse it to a JavaScript object.
You can import a JSON file using the require from the CommonJS module loader like this:
const package = require('./package.json')
package.version
// 3.5.0
Use the @supercharge/fs Package
I’m the maintainer of the @supercharge/fs package providing convenient file system utilities. The @supercharge/fs package comes with a handy Fs.readJson(path) method. the Fs.readJson method reads and parses the content of a JSON file and returns the resolved JavaScript value:
import Fs from '@supercharge/fs'
const package = await Fs.readJson('package.json')
package.version
// 3.5.0
That’s it!
Mentioned Resources
- @supercharge/fs repository on GitHub
- Node.js docs for the
fsmodule