javascript - JSON stringify converts 0 to null -

i trying convert object json doesn't convert enum 0. when print enum 0 when use inside object becomes null. if use string, instead of integer works.

(function () {     'use strict';     var itemstatus = {         'prepared': 0,         'ongoing': 1,         'finished': 2     };     module.exports = itemstatus; })();  (function () {     'use strict';     var itemstatus = require('./itemstatus');      function itemdetail(detail) {         detail = detail || {};          this.message = detail.message || null;         this.location = detail.location || null;         this.status = detail.status || null;         this.date = detail.date || null;      }      module.exports = itemdetail; })();  (function () {     'use strict';      var itemdetail = require('./itemdetail');     var itemstatus = require('./itemstatus');      function item(item) {          item = item || {}          this.name = item.name || null;         this.details = item.details || [];         this.isfinished = item.isfinished || null;         this.finishdate = item.finishdate || null;      }      item.prototype.adddetail = function(message, location,date,status) {          if (this.isfinished) {             this.isfinished = false;         }          console.log('status: ' + status); //prints 0 correctly         var detail = new itemdetail({             message: message,             location: location,             date:date,             status:status          });          this.details.push(detail);         if (status === itemstatus.finished) {             this.isfinished = true;             this.finishdate = date;         }     };       module.exports = item; })(); 

failing test

var should = require('should');  var item = require('../lib/models/item'); var itemdetail = require('../lib/models/itemdetail'); var itemstatus = require('../lib/models/itemstatus');   describe('item detail test:', function() {    this.enabletimeouts(false);       var myitem = new item({         name: 'something',     });      myitem.adddetail('something happened','ny',1212122,itemstatus.prepared);     myitem.adddetail('another thing','ny',1412122,itemstatus.ongoing);     myitem.adddetail('it done','ny',1212122,itemstatus.finished);       it('should print json', function() {         myitem.name.should.eql('something');         console.log(myitem.details[0].status);         myitem.details[0].status.should.eql(itemstatus.prepared);         console.log(json.stringify(myitem));     }); }); 

when printed item shows following

{"name":"something","details":[{"message":"something happened","location":"ny","status":null,"date":1212122},{"message":"another thing","location":"ny","status":1,"date":1412122},{"message":"it done","location":"ny","status":2,"date":1212122}],"isfinished":true,"finishdate":1212122} 

you problem not related json stringify .

the line this.status = detail.status || null; converts 0 null.
because 0 falsy this.status set null detail.status being 0.

you can solve problem either starting itemstatus 1 or not using this.status = detail.status || null;

so either use:

var itemstatus = {     'prepared': 1,     'ongoing': 2,     'finished': 3 }; 

or test way:

this.status = detail.status; if( this.status !== 0 && !this.status) {   this.status = null; }