How to Check if a Variable Exists and is Initialized in JavaScript

General Discussions
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With about a decade dabbling in JavaScript, I can confidently say the most universal safeguard is:

if (typeof myVar !== 'undefined') {
  console.log("It exists!");
}

This typeof check is super safe because it doesn’t blow up even if myVar was never declared. It’s my default when building robust javascript check if variable exists logic — especially when I want to avoid those ugly reference errors that can halt execution. Whether you’re working across modules or loose scripts, this one’s reliable.