Interactive web pages with javascript: chapter 'Perform Selecting Elements': Getting error 'taskInput is not defined'

I just tried it with the workspace. It worked for me. THe only thing i can think of is that you might be running the code in a different context. I get that error is I change the context (there's a drop down box) for the page using the console (see https://developer.chrome.com/devtools/docs/console#frame-selection).

Not sure what you mean by context, but I got the code to work (w/out any changes) by copypasting it into an external editor and previewing it locally. So it seems there's something going on with your editor.

When code executes on a different frame, variables can seem to disappear. Occasionally, the frame is set to an iframe or seems to run into complications with chrome plugins. You can see the page but there are multiple possible frames, and the code you run via the console is isolated from your page. If i switch contexts on the console (a plugin creates a second context accessible via the console tools), the variable (named x) is present and then disappears completely

x;
<input id=​"new-task" type=​"text">
x;
VM202:1 Uncaught ReferenceError: x is not defined(…)