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<!DOCTYPE html>
<html>
<head>
<title>Ejemplo de JavaScript</title>
<meta charset="UTF-8">
</head>
<body>
<script>
let vec = [10, , 30, , 50];
document.write('Recorredo del vector con un for clásico<br>');
for (let f = 0; f < vec.length; f++) {
document.write(vec[f] + '-');
}
document.write('<br>');
document.write('Recorredo del vector con un for in<br>');
for (let indice in vec) {
document.write(vec[indice] + '-');
}
</script>
</body>
</html>