TypeScript Get Object {_object: Array(0)} pushing tab using Object.assign in the console.log

I have a strange problem and I can’t figure out why. I load JSON files to fill my Object “Contest” in TypeScript. I use Object.assign for that. I can see very clearly all the information, but i found difference when i compare it in the console with an another Object not fill from my Json files, so without my Object.assign.

 var core = new Core
  var core2 = new Core
  core2.add(new Contest("test", "youpi", 0))
  core2.add(new Contest("seb", "youpi1", 0))
  readandwrite.getDirectories(readandwrite.getPath(), function (err, content) {
    for (var i = 0, l = content.length; i < l; i++) {
      if ((content[i].slice(-5)).localeCompare(".json") == 0) {
        readandwrite.getJsonFromFile(content[i], function (err, content) {
          var temp = new Contest("", "", 0)
          console.log(temp)
          core.add(Object.assign(temp, content))
        })
      }
    }
  })
  console.log(core)
  console.log(core2)

My function add

    add(value: Contest) {
        this._contest.push(value)
  }

ll the datas load fine, but as you can see, on my object filled with Object.assign (The first one on the picture : Core {_contest: Array(0)}) the array _contest is equal to zero, while the 3 tables and the datas are there. And because of that, I can’t access the values in my charts, it says my values are undefined. Without use Object.assing, we can see “Core {_contest: Array(2)}” and i can acces to my datas. Hope you will understand my explanation …