Why is code after [removed]() not executed?

Question

I have the follwing JavaScript.

Answer 1

Because calling document.write implicity calls document.open, which clears the document on which it has been called:

If a document exists in the target, this method clears it

After the call to document.write, the element you're trying to get a reference to no longer exists in the DOM, and an error is thrown. If you look in the error console it should be something along the lines of the following:

TypeError: Cannot read property 'txt1' of undefined