Try it Editor: With "use strict":

Edit This Code :


<!DOCTYPE html>
<html>
<body>

<h2>With "use strict":</h2>
<h3>Using a variable without declaring it, is not allowed.</h3>

<p>Activate debugging in your browser (F12) to see the error report.</p>

<script>
"use strict";
x = 3.14;    // This will cause an error (x is not defined).
</script>

</body>
</html>

Result :