1/(?:[^[#\s\\]+|\\(?:[\S\s]|$)|\[\^?]?(?:[^\\\]]+|\\(?:[\S\s]|$))*]?)+|(\s*#[^\n\r\u2028\u2029]*\s*|\s+)([?*+]|{[0-9]+(?:,[0-9]*)?})?/g 2/{[0-9]+}?/g 3{123} 4{a} 5f{a} 6f 7SyntaxError 8SyntaxError 9