Filter repeater by a number

I’ve followed the training tutorial on dynamically filtering repeater widgets based on text a user types into a text field. I used a function like this and it worked great for text: [[Item.Author.toLowerCase().indexOf(This.text.toLowerCase()) >= 0]]

But it doesn’t work when I’m searching an item in my repeater that is a number rather than text. How can I change the function to dynamically filter for numbers as well?