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<body>
<script type="module" src="script.js"></script>
</body>
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\vert % Gives: |
\Vert % Gives: ||
https://tex.stackexchange.com/questions/151984/double-vertical-bar-notation
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<!DOCTYPE html>
<html>
<body>
<h2>JavaScript in HTML</h2>
<p id="demo">Before JavaScript</p>
<script>
document.getElementById("demo").innerHTML = "After JavaScript";
</script>
</body>
</html>