weird part 37 — ‘this’ keyword point to window or object?

#window — global object

function a (){
 console.log(this)//window - global variable
  this.newVariable = 'hello'
}
var b = function(){
 console.log(this)
}
a();//window
console.log(newVariable)
b(); //window

#object

var c = {
 name:'C object',
  log:function(){
   console.log(this)
  }
}
c.log(); //'this' is object{name: "C object", log: ƒ}

# common error

var c = {
 name:'C object',
  log:function(){
   this.name = 'updated c objet name'
   console.log('this 1',this)
    
    var setname = function(newname){
     this.name = newname; // pointing to window
    }
    setname('updated again! overwrite c object ')
    console.log('this 2',this) // window.name 
  }
}
console.log(c.name)
c.log(); //{name: "C object", log: ƒ}

• internal function ‘setname’ is pointing to window

# how this keyword can point to this c object? — var self = this

var c2 = {
  name:'C2 object',
  log:function(){
   var self = this; //mutate
    
    self.name = 'updated c2 objet name'
    console.log('this 1',this)
    
   var setname = function(newname){
      self.name = newname;
    }
    setname('updated again! c2 object ')
    console.log('self',self) //{name: "updated again! c2 object ", log: ƒ}
    console.log('this',this) //{name: "updated again! c2 object ", log: ƒ}
  }
}
console.log(c2)
c2.log();

• var self = this — pointing the whole object ‘C’