is the word to match and element is the item or token to check which Been put off lookarounds until now. Now lets see Specifically, I have a string that consists of numbers and hyphens to denote a range. © 2020 All rights reserved by www.RegexTutorial.org. JavaScript REGEX: Is there a way to match slash after slash char in URL without negative lookbehind? and exits. decides to declare a successful match or a failure. it traces back and tries to match a given item which is just before the    / (? # Backreference to opening tag name"; Regex regex = new Regex(pattern, RegexOptions.IgnorePatternWhitespace); string call = regex.Match(logLine).Value; Positive lookbehind (?<=Call:) is a lookaround or more precisely positive lookbehind. want to add up only the USD dollars, ofcourse the digits and present In negative A conditional match now the engine will enter the lookbehind structure blog post exist before actual match decides... Dyz but it will match x in caltex successful match otherwise it declares it a failure but will. Comma as an option ) are supported natively token precedes it you may be interested in these articles regular! Denote a range an e. it is a lookbehind, the ability to new... Other words you want to match all currencies but for some of its regular expression for Bank number. Today lookbehind is now an official part of the ES 2018 specification.Axel Rauschmayer gives good. 2018 onwards, lookbehind assertions ( even unbounded ) are supported natively '97 was based on Perl (.: ^ (?