Question

Which browsers support multi-line strings?

"foo \
bar"

As usual, my main suspect for not supporting it is IE.
Which IE version is the first that supports it?

Answer 1

All current versions of the major browsers accept multi-line strings.

Note: this technique is apparently not in
compliance with browser standards; however, it works out fine when
tested across all current versions of the major browsers.

• Some online tools such as JSLint don’t allow it
• Multi-line strings can be dangerous in JavaScript because all hell breaks loose if you accidentally put a whitespace in between the escape character (\) and a new line. (@ripper234 comment)

Multiline String literals are disallowed by the Google Style Guide.