1. Object attribute deletion
function fun(){this.name = 'mm';}var obj = new fun();console.log(obj.name);//mmdelete obj.name;console.log(obj.name); //undefined2. Variable deletion
var name = 'lily';delete name;console.log(name); //lily
Can't delete variables directly with delelte
3. The variables in the prototype chain cannot be deleted.
fun.prototype.age = 18;delete obj.age;console.log(obj.age) //18