Confused on how notes = JSON.parse(noteString); - json

Question

var addnote = function (title, body) {
var notes = [];
var note = {
title: title,
body: body
}
need explanation on the two lines under try
try {
var noteString = fs.readFileSync("data.json");
notes = JSON.parse(noteString);
} catch (e) {
}
And explanation on how duplicateNotes works ..
var duplicateNotes = notes.filter(function(note){
return note.title === title
})
if (duplicateNotes.length === 0) {
notes.push(note);
fs.writeFileSync("data.json", JSON.stringify(notes));
}
}

Answer 1

JSON.parse converts a JSON object to String.
{
field1:field1Value,
field2:fieldValue
}
If this is in Json format you can access it's elements using JSONObjectName.fieldName
But,if it's converted to String it looses it's JSON properties. You can't access fields in same way. Output will act like String.
need explanation on the two lines under try
var noteString = fs.readFileSync("data.json");
There are two kinds of response back asynchronous and synchronous. Synchronous call is like you will not start playing until you get a pass and score a goal. But, Asynchronous call is like you start playing with your friend but, you run near him and, there is a promise you won't shoot until you get the ball.
readFileSync will read the file and the next line will wait until it gets the pass.JSON.parse() will convert file content to JSON object.
And explanation on how duplicateNotes works ..
var duplicateNotes = notes.filter(function(note){
return note.title === title
})
Whenever a match is found , that element in notes will be pushed to duplicate note. That's all.