I have a json file that looks something like this. I need to write a JS code that will parse through this file and read specific elements of the file like sensor_state of the first element and write to the specific element like change the sensor_state of "sensor_id": "302CEM/lion/light1" to on. this is what i have tried. I had a few thoughts on how to to go about it. trying to treat it like an array, sensor_state[0] will mean the first group, sensor_state[1] would mean the second one and so on. the other way is to have a name i.e light_1 before each group/object to have code that says sensor_data[light1][sensor_state] = "off" but i am unable to structure the json file to do either. Any suggestions

            {
                "sensor_data": [

                    {
                        "sensor_id": "302CEM/lion/light1",
                        "sensor_state": "off"
                    },
                    {
                        "sensor_id": "302CEM/lion/light2",
                        "sensor_state": "off"
                    }
                ]
            }

            const fs =
            require('fs');

            var data = []

            //To Read from the JSON File, dont know if this still needed

            fs.readFile('datajson.json', (err,data) => {

            if (err) throw err;

            var sensor = JSON.parse(data);

            var stringy = JSON.stringify(data)

            console.log(stringy.sensor_state[0]);

            }
            )

• In order to process your JSON, it's much easier to do it just after JSON.parse instead of working with the string that JSON.stringify returns.
• And to write your file after processing. You first convert your object into a string using JSON.stringify. Then call fs.writeFile to actually write the content

Your code will look like this

const fs = require('fs');
const fileName = './data.json';

fs.readFile(fileName, (errRead, content) => {
  if (ererrReadr) throw errRead;

  let data = JSON.parse(content);

  // Change the "sensor_id" of the first item in "sensor_data"
  data.sensor_data[0].sensor_id = 'this is a new ID';

  // Write back new JSON
  fs.writeFile(fileName, JSON.stringify(data), errWrite => {
    if (errWrite) throw errWrite;

    console.log('New data has been saved');
  });
});

Note

I had a few thoughts on how to to go about it. trying to treat it like an array

It is an array, so it only makes sense to treat it like one.