default parameter in javascript

//ES5 

function person(name,age,profession){

    profession===undefined?profession="engineer":profession=profession;

    this.name = name;

    this.age = age;

    this.profession = profession;

}

var lokman = new person('lokman',32);//In javascript no need to provide all the parameter when a function                                                                 is called.

console.log(lokman);

//ES6

function person(name,age,profession='engineer'){

    this.name = name;

    this.age = age;

    this.profession = profession;

}

var lokman = new person('lokman',32);