You could try something like this:
var a = getField("Component");
var b = getField("Serial_Number");
var c = getField("Number");
var d = getField("Details");
if ((a.value =="") || (b.value =="") || (c.value =="") || (d.value =="")){
app.alert("Please complete all required fields");
}
else // continue with the rest of your script
If you have a lot of required fields, and you do not want to reference them in your script, you need to create a for loop that will search your form for all required fields and then do something.
Here is an example: