applescript Web Scraping script not working

I am trying to learn how to build a web scraper to improve my productivity at work. I found a site that gives an example and step by step guide on how to build a rudimentary scraper but when I put the code into my script editor I get the error "the variable input is not defined." number -2753 from "input". the code looks like this:

to getInputByClass(theClass, num) -- defines a function with two inputs, theClass and num
    tell application "Safari" --tells AS that we are going to use Safari
        set input to do JavaScript "document.getElementsByClassName('" & theClass & "')[" & num & "].innerHTML;" in document 1
    end tell
    return input
end getInputByClass

getInputByClass("r", 0)

Any help on how to fix the code would be greatly appreciated.