//字串
var personString = '{"name":"Andrew","age":25}';
console.log( typeof personString);//string
//轉換為物件
var person = JSON.parse(personString);

console.log(typeof person);//object
console.log(person);//{ name: 'Andrew', age: 25 }

const fs=  require
 
('fs');

//物件
var originalNote = {
  title:'some title',
  body:'some body'
};
//轉換為字串
var originalNoteString = JSON.stringify(originalNote);
//字串寫入到檔案中
fs.writeFileSync('notes.json',originalNoteString);
//讀取檔案
var noteString = fs.readFileSync('notes.json');
//轉換為物件
var note = JSON.parse(noteString);
console.log(typeof
 
 note);//object
console.log(note.title);//some title

> node json.js

string
object
{ name: 'Andrew', age: 25 }
object
some title