How to select html nodes by ID with jquery when the id contains a dot?

You don't need to escape anything if you use document.getElementById:

$(document.getElementById('strange.id[]'))

getElementById assumes the input is just an id attribute, so the dot won't be interpreted as a class selector.

One variant would be this:

$("input[id='SearchBag.CompanyName']")

@Tomalak in comments:

since ID selectors must be preceded by a hash #, there should be no ambiguity here

“#id.class” is a valid selector that requires both an id and a separate class to match; it's valid and not always totally redundant.

The correct way to select a literal ‘.’ in CSS is to escape it: “#id\.moreid”. This used to cause trouble in some older browsers (in particular IE5.x), but all modern desktop browsers support it.

The same method does seem to work in jQuery 1.3.2, though I haven't tested it thoroughly; quickExpr doesn't pick it up, but the more involved selector parser seems to get it right:

$('#SearchBag\\.CompanyName');