Check if an object contains a property called format in Javascript

I have an array of movie objects in a web application, and each object has properties for title(string),release year(int),rating(int) and genre(an array of string e.g ['Action','Sci-Fi],now some of the movie objects got a property for format(string) while others don’t.All I need is help iterating through these objects and checking which objects don’t have a format property and add the property to these objects and set the values with Film for those that do not… Here is the js code i tried so far

var fractured={
  title:"Fractured",
  release:2019,
  rating:8,
  format:"digital",
  genre:[
    "Mystery","Sci-Fi","Western"]
};
var countdown={
  title:"Countdown",
  release:2018,
  rating:5,
  genre:["Sci-Fi","Mystery","Western"]
}
var bloodshot={
  title:"Bloodshot",
  release:2020,
  rating:6,
  format:"digital",
  genre:["Sci-Fi","Action"]
}
var revenant={
  title:"Revenant",
  release:2015,
  rating:3,
  genre:["History","Western","Action"]
}
var crisis={
  title:"Crisis",
  release:2016,
  rating:10,
  genre:["Action","Drama","Reality"]
}
var life={
  title:"Life",
  release:2017,
  rating:9,
  format:"digital",
  genre:["Sci-Fi","Action","Mystery"]
}
var nmovies=new Array(fractured,life,crisis,revenant,bloodshot,countdown);

//This line outputs the title property of the first object in nmovies;
console.log(nmovies[0].title);

//this is the iteration that needs to check if an object has a format property and add it with the value 'Film'
nmovies.forEach(myfunction());

function myfunction(item, index){
//Code to check please
}

Thank you for your input.

Answer

I am new to JavaScript but hopefully that works.

function myfunction(item, index) {
  if (!item.hasOwnProperty("format")) {
    item.format = "Film";
  }
}