Javascript Node.js JSON.parse数组

Question

I'm taking a course on udemy and i'm really confused on how notes = JSON.parse(notesString) is an array when it's suppose to be an object (right?) since JSON.parse makes it an object.

var addNote = (title, body) => {
  var notes = []; // Create empty array
  var note = { // Fetch user input
    title,
    body
  };
  try {
    var notesString = fs.readFileSync("notes-data.json"); //  Get current notes
    notes = JSON.parse(notesString); // convert current notes into object
    console.log("try:", notes.constructor)
  }catch(e){

  }
  console.log(notes)
  notes.push(note);
  fs.writeFileSync("notes-data.json", JSON.stringify(notes));
};

Answer 1

JSON.parse() is required over there because the output of a fs operation is a string which we need to convert into an object in order to access it properly. The data inside it is a JSON Array as a result we are able read it. Add try catch around the JSON.parse because if the data is not of JSON type then it will cause an error.

Answer 2

If JSON in file notes-data.json contains JSON-array, ie some content like

[{"one":1}, {"two":2}]

You will get array from JSON.parse method.

Answer 3

If JSON in file notes-data.json contains JSON-array, ie some content like

var data = "[{"one":1}, {"two":2}]";
var result = JSON.parse(data);
console.log(result)