- Trending Categories
Data Structure
Networking
RDBMS
Operating System
Java
iOS
HTML
CSS
Android
Python
C Programming
C++
C#
MongoDB
MySQL
Javascript
PHP
- Selected Reading
- UPSC IAS Exams Notes
- Developer's Best Practices
- Questions and Answers
- Effective Resume Writing
- HR Interview Questions
- Computer Glossary
- Who is Who
How to check for “undefined” variable in JavaScript?
On getting the result of the following, you can find whether a variable is ‘undefined’. If the result is “false”, it means the variable is undefined.
Here, the variable results in “True”
Example
Live Demo
<html>
<body>
<script>
var res = 10;
if(res) {
document.write("True");
} else {
document.write("False");
}
</script>
</body>
</html>
Updated on 30-Jul-2019 22:30:21
- Related Questions & Answers
- How to check for null, undefined, or blank variables in JavaScript?
- Setting a default variable value to undefined in a function - JavaScript?
- Undefined in JavaScript
- How to check if a variable exists in JavaScript?
- How to check a not-defined variable in JavaScript?
- Is there is a standard function to check for null, undefined, or blank variables in JavaScript?
- JavaScript undefined Property
- How to check if a variable is NaN in JavaScript?
- How to check if a variable is boolean in JavaScript?
- How to check if a variable is an integer in JavaScript?
- How to check if a variable is an array in JavaScript?
- Undeclared vs Undefined? In JavaScript
- How to remove blank (undefined) elements from JavaScript array - JavaScript
- How to check for 'undefined' or 'null' in a JavaScript array and display only non-null values?
- JavaScript - array undefined element count
Advertisements