how to use an object in javascript code example

Example 1: how to create object js

function person(fname, lname, age, eyecolor){
  this.firstname = fname;
  this.lastname = lname;
  this.age = age;
  this.eyecolor = eyecolor;
}

myFather = new person("John", "Doe", 50, "blue");
document.write(myFather.firstname + " is " + myFather.age + " years old.");

Example 2: create object javascript

let voleur = {
     action     : () =>console.log ('Coup de dague fatal') ,
     crie      : ('pour la horde!!!!') ,
     coupfatal :()=> console.log ('coup dans le dos')

}

voleur.action() ;
voleur.coupfatal() ;
console.log(voleur.crie) ;