CODEWITHSUNDEEP
javascript
Filip Grkinic
Filip Grkinic

Reputation: 130

Adding properties to object with function call in Javascript

Console log is giving me "undefined". I can't find a way to add object properties inside myBox object with "addBook" function. Maybe I'm just calling it wrong, but I think it should be correct way to do it. 

  function addBook (box, name, writer) {
  box["# of Books"]++;
  box["book" + box["# of Books"]] = {title: name, author: writer};
  }

  var myBox = {
  height: 10,
  width:50,
  volume:400
  };


  addBook(myBox, "Javascript Ninja", "Ninja");
  console.log(myBox.book1.title);

Upvotes: 0

Views: 38

Answers (1)

Denys Séguret
Denys Séguret

Reputation: 382092

The problem is you try to increment an undefined value, thus you get NaN.

Simply initialize your counter :

 function addBook (box, name, writer) {
  box["# of Books"]++;
  box["book" + box["# of Books"]] = {title: name, author: writer};
  }

  var myBox = {
  height: 10,
  width:50,
  volume:400
  };
  myBox["# of Books"]=0; // <-- there


  addBook(myBox, "Javascript Ninja", "Ninja");
  console.log(myBox.book1.title);

When you encounter such a problem, you should first debug it yourself, seeing the values step by step. Read Debugging JavaScript.

Upvotes: 1

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