Welcome to the Treehouse Community

The Treehouse Community is a meeting place for developers, designers, and programmers of all backgrounds and skill levels to get support. Collaborate here on code errors or bugs that you need feedback on, or asking for an extra set of eyes on your latest project. Join thousands of Treehouse students and alumni in the community today. (Note: Only Treehouse students can comment or ask questions, but non-students are welcome to browse our conversations.)

Looking to learn something new?

Treehouse offers a seven day free trial for new students. Get access to thousands of hours of content and a supportive community. Start your free trial today.

JavaScript JavaScript Loops, Arrays and Objects Tracking Multiple Items with Arrays Useful Array Methods

Weird Error

var listItem = ['Apple', 'Banana', 'Mango', 'Orange']; var search;

while (true) { search = prompt("Search for a product, type 'list' to show all products and 'quit' to exit "); search = search.toLowerCase(); if (search === 'quit') { break; } else if (search === 'list') { document.write( listItem.join(', ')); } else { if ( listItem.indexOf(search) > -1) { document.write('<p>' + "Yes we have " + search + " in our product list " + '</p>'); } else { document.write('<p>' + "Sorry we don't have " + search + " in our product list " + '</p>'); } } }

getting this error in the Console Uncaught TypeError: Cannot read property 'toLowerCase' of null

1 Answer

Steven Parker
Steven Parker
221,326 Points

To avoid this, check that "search" is not null (or not "falsey") before you perform the lower case conversion. (You may want to "break" if it is).

Additionally, to be able to match with your list of items, you will need to convert them also (or store them as lower case).

Thanks for your help, first alphabet of array elements were in upper case