Difference Between 'var A = B' And 'this.a = B'

I have been dealing and learning about Objects and OOP in JS in the past few days and I good a basic understanding how they work now. One thing that bothers me, and I have problems

Solution 1:

Nope youre wrong. var adds a property to the current functional context:

obj={
  add:function(){
    var plane="test";
    this.bird="test2";
  }//plane gets deleted right here as it isnt used anymoreand it was never part of obj
};

obj.add();
obj.plane;//never existed
console.log(obj.bird);