I have this code but I need to be able to input either lower case or upper case and get a result. For example I want to enter history and get back History Book and also enter HISTORY and get back History Book.

I there a way I can do this.

Here is my code.
<script type="text/javascript">
function show_prompt()

var book=prompt("Enter a book");

if(book == "history" ){
document.write("<b>History Book</b>");
}else if( book == "maths" ){
document.write("<b>Maths Book</b>");
}else if( book == "economics" ){
document.write("<b>Economics Book</b>");
document.write("<b>Unknown Book</b>");



<input type="button" onclick="show_prompt()" value="click here to find out the book you need" />