When should you not use regex?
3 Answers. Don’t use regular expressions when: the language you are trying to parse is not a regular language, or. when there are readily available parsers specifically made for the data you are trying to parse.
When should we use regex?
Regular expressions are used in search engines, search and replace dialogs of word processors and text editors, in text processing utilities such as sed and AWK and in lexical analysis. Many programming languages provide regex capabilities either built-in or via libraries, as it has uses in many situations.
Is it good practice to use regex?
Yes – regular expressions work very well for input validation. However, often times it’s a very good idea to abstract these things away as much as possible as other methods – or even sometimes special validator objects.
Is regex slow JavaScript?
My experience shows that most of the time developers focus on correctness of a regex, leaving aside its performance. Yet matching a string with a regex can be surprisingly slow. So slow it can even stop any JS app or take 100\% of a server CPU time causing denial of service (DOS).
Why should you avoid complicated regular expressions?
Complicated regular expressions that aren’t well documented will just lead to confusion the next time you or another developer on your team comes across it. Many regex interpreters allow you to specify a flag to ignore whitespace.
Why don’t we use regular expressions in C++?
Regular expressions do not support this working style very well. One “run” of a regular expression is effectively an atomic operation. It’s hard to observe stepwise execution in a debugger. It’s too easy to write a regular expression that accidentally accepts more input than you intend.
Is it true that regexes are slow?
And yes, regexes can be extremely extremely slow compared to using simple functions. And not just slow, but the performance of the regex engine can be totally unpredictable when faced with arbitrary (user-supplied) inputs.
Why don’t people use regex for modern patterns?
Modern patterns have almost nothing in common with the primitive things you were taught in your finite automata class. Regexes are a great tool, but people think “Hey, what a great tool, I will use it to do X!” where X is something that a different tool is better for (usually a parser).