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JavaScript: Delete a property from an object and print before or after deleting

JavaScript Object: Exercise-2 with Solution

Write a JavaScript program to delete the rollno property from the following object. Also print the object before or after deleting the property.
Sample object:
var student = {
name : "David Rayy",
sclass : "VI",
rollno : 12 };

Sample Solution:-

HTML Code:

<!DOCTYPE html>
<html>
<head>
<meta charset=utf-8 />
<title>Delete a property from an object</title>
</head>
<body>
</body>
</html>

JavaScript Code:

var student =  { 
  name : "David Rayy", 
  sclass : "VI", 
  rollno : 12  };
console.log(student);
delete student.rollno;
console.log(student);

Sample Output:

{"name":"David Rayy","sclass":"VI","rollno":12}
{"name":"David Rayy","sclass":"VI"}

Flowchart:

Flowchart: JavaScript - Delete a property from an object and print before or after deleting.

Live Demo:

See the Pen javascript-object-exercise-2 by w3resource (@w3resource) on CodePen.


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JavaScript: Tips of the Day

What is the !! (not not) operator in JavaScript?

Converts Object to boolean. If it was falsey (e.g. 0, null, undefined, etc.), it will be false, otherwise, true.

!oObject  // inverted boolean
!!oObject // non inverted boolean so true boolean representation

So !! is not an operator, it's just the ! operator twice.

Real World Example "Test IE version":

const isIE8 = !! navigator.userAgent.match(/MSIE 8.0/);  
console.log(isIE8); // returns true or false 

If you =>

console.log(navigator.userAgent.match(/MSIE 8.0/));  
// returns either an Array or null

But if you =>

console.log(!!navigator.userAgent.match(/MSIE 8.0/));  
// returns either true or false

Ref: https://bit.ly/3ezKiqB