Regular expression, why the result is the following? - Js

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let text = "titanic";
let myRegex = /t[a-z]*i/; // Change this line
let result = text.match(myRegex); //gives "titani" -- why?

What I have tried:

looking for the '/t' explanations.

Posted 10-Mar-19 21:09pm

Member 14105304

Updated 10-Mar-19 23:42pm

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OriginalGriff · Answer 1 · 2019-03-10T21:20:00

Solution 1

Because it matches.
"*" is "zero or more" so "ti" matches, but so does "titani".
If you want the shortest match, you have to tell the regex that:

/t[a-z]*?i/

Posted 10-Mar-19 21:20pm

OriginalGriff

Comments

Member 14105304 11-Mar-19 3:25am

i mean why it did not give "titanic", c is included between a-z..?

OriginalGriff 11-Mar-19 4:17am

Because your match expression ends with an "i" not a "c".
Regex is a *pattern matching* system - and your expression says "Match anything that starts with a 't', followed my zero or more of any alphabetic character, and ends with an 'i' - ignore anything after that".

Go here:
http://www.ultrapico.com/Expresso.htm
and get a copy of Expresso - it's free, and it examines, generates, and tests Regular expressions. It also tries to explain them in "near English" if you enter one. If you are going to play with Regexes, it's a godsend!

Member 14105304 11-Mar-19 4:29am

ohhh.. it starts from 't' till 'i', i thought i is the flag..
gotch'a! thnx a lot! =]

OriginalGriff 11-Mar-19 4:50am

You're welcome!

Patrice T · Answer 2 · 2019-03-10T23:42:00

Just a few interesting links to help building and debugging RegEx.
Here is a link to RegEx documentation:
perlre - perldoc.perl.org[^]
Here is links to tools to help build RegEx and debug them:
.NET Regex Tester - Regex Storm[^]
Expresso Regular Expression Tool[^]
RegExr: Learn, Build, & Test RegEx[^]
Online regex tester and debugger: PHP, PCRE, Python, Golang and JavaScript[^]
This one show you the RegEx as a nice graph which is really helpful to understand what is doing a RegEx: Debuggex: Online visual regex tester. JavaScript, Python, and PCRE.[^]
This site also show the Regex in a nice graph but can't test what match the RegEx: Regexper[^]