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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 reg = /your regexp/g;

alert("Java JavaScript PHP C++ C".match(reg)); // Java JavaScript PHP C++ C

The first idea can be to list the languages with | in-between.

But that doesn’t work right:

let reg = /Java|JavaScript|PHP|C|C\+\+/g;

let str = "Java, JavaScript, PHP, C, C++";

alert( str.match(reg) ); // 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:

  1. Change the order to check the longer match first: JavaScript|Java|C\+\+|C|PHP.
  2. Merge variants with the same start: Java(Script)?|C(\+\+)?|PHP.

In action:

let reg = /Java(Script)?|C(\+\+)?|PHP/g;

let str = "Java, JavaScript, PHP, C, C++";

alert( str.match(reg) ); // Java,JavaScript,PHP,C,C++