Find programming languages
There are many programming languages, for instance Java, JavaScript, PHP, C, C++.
Create a regexp that finds them in the string Java JavaScript PHP C++ C
:
let
regexp =
/
your regexp
/
g
;
alert
(
"Java JavaScript PHP C++ C"
.
match
(
regexp)
)
;
// Java JavaScript PHP C++ C
The first idea can be to list the languages with |
in-between.
But that doesn’t work right:
let
regexp =
/
Java|JavaScript|PHP|C|C\+\+
/
g
;
let
str =
"Java, JavaScript, PHP, C, C++"
;
alert
(
str.
match
(
regexp)
)
;
// Java,Java,PHP,C,C
The regular expression engine looks for alternations one-by-one. That is: first it checks if we have Java
, otherwise – looks for JavaScript
and so on.
As a result, JavaScript
can never be found, just because Java
is checked first.
The same with C
and C++
.
There are two solutions for that problem:
- Change the order to check the longer match first:
JavaScript|Java|C\+\+|C|PHP
. - Merge variants with the same start:
Java(Script)?|C(\+\+)?|PHP
.
In action:
let
regexp =
/
Java(Script)?|C(\+\+)?|PHP
/
g
;
let
str =
"Java, JavaScript, PHP, C, C++"
;
alert
(
str.
match
(
regexp)
)
;
// Java,JavaScript,PHP,C,C++