Node Js Acessing a Jason File - node.js

Question

still new to JSON and while ive searched the net and created a function to create a init file if none exists i'm coming up blank for search and retrive the data of the new existing file or how I add new entries or update new entries
so far i can do a read file and export the resits in a console log so i know the assignment work, its a global variable so the data should persist out of the read file loop but when i try and access it later to make the local array i'll pull data from and use for updating later it reads as undefined.
fs.readFile(path, 'utf8', (error, data) => {
if(error){
console.log(error);
return;
}
//console.log(JSON.parse(data));
JSONData = JSON.parse(data);
for (let i = 0; i < JSONData.length; i++) {
console.log(i+": ["+JSONData[i].unique+"] "+JSONData[i].name);
}
});//fs.readFile
var playerKey = "KuroTO";
playerKey = playerKey.toLowerCase();
for (let i = 0; i < JSONData.length; i++) {
if (JSONData[i].unique.toLowerCase() == playerKey){
console.log("["+i+"] "+JSONData[i].unique.toLowerCase()+": "+playerKey);
PlayerCard1.push(JSONData[i].userid);//0
PlayerCard1.push(JSONData[i].username);//1
PlayerCard1.push(JSONData[i].unique);//2
PlayerCard1.push(JSONData[i].name);//3
PlayerCard1.push(JSONData[i].avatarurl);//4
PlayerCard1.push(JSONData[i].level);//5
PlayerCard1.push(JSONData[i].Rank);//6
PlayerCard1.push(JSONData[i].henshined);//7
PlayerCard1.push(JSONData[i].Strength);//8
PlayerCard1.push(JSONData[i].Perception);//9
PlayerCard1.push(JSONData[i].Endurance);//10
PlayerCard1.push(JSONData[i].Wisdom);//11
PlayerCard1.push(JSONData[i].Intelligence)//12;
PlayerCard1.push(JSONData[i].Luck)//13;
PlayerCard1.push(JSONData[i].Agility)//14;
PlayerCard1.push(JSONData[i].Flexability)//15;
PlayerCard1.push(JSONData[i].RatedSpeed)//16;
};//if unique matches
};//for
this is ther psudo code concept im trying to do
if (JSONData.stringify.unique == {SearchUID}){toonname = JSONData.stringify.name;}
as i understand it you cant really apend just rewrite the file over again with new data and i think i can figure that out on my own once i cand figure out how to real the file into an array i can search like above

Answer 1

To read JSON, simply require the file.
JSON:
{
"key": "H"
}
JS:
let jsonFile = require("./path/to/json");
console.log(jsonFile.key); // H
Editing is just as simple.
let jsonFile = require("./path/to/json");
jsonFile.key = "A"
console.log(jsonFile.key) // A
Saving edits requires use of FileSystem:
const fs = require("fs")
let jsonFile = require("./path/to/json");
jsonFile.key = "A"
// first argument is the file path
// second argument is the JSON to write - the file is overwritten already
// due to above, so just JSON.stringify() the required file.
// third argument is an error callback
fs.writeFile("./path/to/jsonFile", JSON.stringify(jsonFile), (err) => {
if (err) throw new Error(err);
});
This can also be used to slightly clean up your current init function if you wanted, but that's up to you of course.