JavaScript is a case-sensitive language. This means that the language keywords, variables, function names, and any other identifiers must always be typed with a consistent capitalization of letters.
So the identifiers Time and TIME will convey different meanings in JavaScript.
NOTE − Care should be taken while writing variable and function names in JavaScript.
Example
The following example shows JavaScript is a case-sensitive language:
<!DOCTYPE html>
<html>
<body>
<h3>My favorite subject</h3>
<p id="demo"></p>
<script>
var subject, Subject;
subject = "Java";
Subject = "Maths";
document.getElementById("demo").innerHTML = subject;
</script>
</body>
</html>