JavaScript isset() function
javascript, php
Solution
When javascript variables are not declared and you try to call them, they return `undefined`, so you can do:
`if (typeof sessionvalue == "undefined" || sessionvalue == null)`
Problem
How to check `isset` in javascript. I have used in the following way. ``` var sessionvalue = document.getElementById('sessionvalue').value; if(Here I have to check if isset the sessionvalue or not){ if(sessionvalue == "" || sessionvalue == null) { document.getElementById('sessionvalue').style.borderColor="red"; return false; } else { document.getElementById('sessionvalue').style.borderColor="#ccc"; } } ```