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How to check if a variable exists in JavaScript?
To check if a variable exists in JavaScript, you need to check it against null as in the following code. Here, we’re checking the existence of variable myVar −
<html>
<body>
<script>
var myVar = 20;
if(myVar !== undefined && myVar !== null) {
document.write("Variable exists");
}
</script>
</body>
</html>
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