I tried to pass to null an instance of class but in vain. Here avatar2 is not delete, why ? console log

class Avatar{
  constructor(name, weapon = "knife", pv = 100){
    this.name = name;
    this.weapon = weapon;
    this.pv = pv;
  }
  attaqueDefault(target){
    if (target.hasOwnProperty('pv'))
      target.pv -= 20;
  }
  attaqueCombine(target){
    if (target.hasOwnProperty('pv'))
      target.pv -= 35;
  }
  destroy(target){
    target = undefined;
  }
}

var avatar = new Avatar("tchod");
var avatar2 = new Avatar("tchod2", ".44");

avatar.destroy(avatar2);