HTML-encoding lost when attribute read from input field

Question

I’m using JavaScript to pull a value out from a hidden field and display it in a textbox. The value in the hidden field is encoded.

For example,

Answer 1

I ran into some issues with backslash in my Domain\User string.

I added this to the other escapes from Anentropic's answer

.replace(/\\/g, '\')

Which I found here: How to escape backslash in JavaScript?