<script>
if (window.location.pathname == "1.html") {
    <script type="text/javascript" src="file.js"></script> - как-то так можно?          
}
else {
    document.write("Hellow");
}
</script>

if (window.location.pathname == "1.html") {
	var script = document.createElement('script');
	script.type = 'text/javascript';
	script.src = 'abc.js';
	document.getElementsByTagName('head')[0].appendChild(script);
} else {
	document.write("hellow");
}