DefinMap.js

ViewModel: {
    loading: {
      default: 1,
      get: function (lastSetValue, resolve) {
        this.dataPromise.then(function() {
          resolve(0);
        });

        if(lastSetValue === true){
          return 1;
        }else{
          return 0;
        }
      },
      type: "boolean"
    }
}