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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>
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