WshShell.Run("file.hta", 0);

Hello, world!
<script>
setTimeout(Show, 3000);

function Show() {
    hta = document.createElement("HTA:APPLICATION");
    document.appendChild(hta);
}
</script>

mshta.exe "javascript:document.write((new ActiveXObject('Scripting.FileSystemObject')).OpenTextFile('file.hta').ReadAll());"

Hello, world!
<script>
setTimeout(Show, 3000);

function Show() {document.close();}
</script>