Is handling of curly braces in javascript regex is the same across all modern browsers?

Curly braces in JavaScript regex is used to denote quantifiers. So writing

a{2,4}

will match aa, aaa and aaaa. But if you mistype this quantifier like this:

x{1,x}

It will match the literal text "x{1,x}", at least in Firefox.

Is this behavior common to modern browsers?

The ECMA standard prohibits this behavior and requires the escaping of the braces.

(Background: I have to write a parser for javascript regexes at work.)

Source: Tips4all