How to add a new key value pair in existing JSON file using Nodejs?

To add a new key-value pair to an existing JSON file using Node.js, you can follow these steps:

1. Read the JSON file and parse its contents.
2. Modify the parsed object by adding the new key-value pair.
3. Write the updated object back to the JSON file.

Here's an example of how you can add a new key-value pair to an existing JSON file named data.json:

data.json (before modification):

{
  "name": "John Doe",
  "age": 30
}

Node.js code:

const fs = require('fs');

// Step 1: Read the JSON file
fs.readFile('data.json', 'utf8', (err, data) => {
  if (err) {
    console.error('Error reading JSON file:', err);
    return;
  }

  try {
    // Step 2: Parse the JSON data
    const json = JSON.parse(data);

    // Step 3: Add a new key-value pair
    json.newKey = 'New Value';

    // Step 4: Write the updated object back to the JSON file
    fs.writeFile('data.json', JSON.stringify(json, null, 2), 'utf8', (err) => {
      if (err) {
        console.error('Error writing JSON file:', err);
        return;
      }
      console.log('Key-value pair added successfully!');
    });
  } catch (err) {
    console.error('Error parsing JSON:', err);
  }
});

After running the code, the data.json file will be modified with the new key-value pair:

data.json (after modification):

{
  "name": "John Doe",
  "age": 30,
  "newKey": "New Value"
}

Make sure to have the data.json file present in the same directory as the script, and replace data.json with the appropriate file path if it's located elsewhere.

Happy Coding! ❤️