Is there a way to create a input prompt box that doesn't have the cancel button, or doesn't allow the user to close the prompt until some value is entered?
Put your promt
inside a while loop and continue asking for input until user gives any.
do{
input = prompt("Give input");
}while(input == null || input == "" );
console.log(input);
[Note : It's a way to fulfill your requirement that I won't suggest as it may annoy user. You can go with regular expression if you want user to complete your form.]