delete

js/script.js

var ara = [1, 2, 3, 4, 5];
delete ara[2];
function funMake() {
for(var i=0; i<ara.length; i++) {
document.write(ara[i] + '<br />');
}
}

var ara = [1, 2, 3, 4, 5];
delete ara[2];
function funMake() {
for(var i=0; i<ara.length; i++) {
document.write(ara[i] + '<br />');
}
}

index.html

<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8" />
<title>New Page</title>
<script src="js/script.js"></script>
</head>
<body>
<script>
funMake();
</script>
</body>
</html>

<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8" />
<title>New Page</title>
<script src="js/script.js"></script>
</head>
<body>
<script>
funMake();
</script>
</body>
</html>