Add property to object JavaScript | Example code

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Use the dot notation to Add property to object in JavaScript. Below code added the foo property to the obj object above with value 1.

obj.foo = 1;

You can also add a property by using the bracket notation:

obj['foo'] = 1;

Both ways do the same but bracket nation can have invalid property identifiers in the string.

Add property to object JavaScript

Simple example code.

<!DOCTYPE html>
<html>
<body>

  <script>

    var obj = { Name: "Joe" };

    obj.Age = 25;

    obj['Country'] =  "USA"
  
    console.log(obj)

  </script>

</body>
</html> 

Output:

Add property to object JavaScript

Is it possible to add dynamically named properties to JavaScript objects?

Answer: Yes, it is possible, see below code.

var data = {
    'PropertyA': 1,
    'PropertyB': 2,
    'PropertyC': 3
};

data["PropertyD"] = 4;

// dialog box with 4 in it
alert(data.PropertyD);
alert(data["PropertyD"]);

Do comment if you have any doubts or suggestions on this JS object topic.

Note: The All JS Examples codes are tested on the Firefox browser and the Chrome browser.

OS: Windows 10

Code: HTML 5 Version

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