I have a situation where I need to test the string if it contains a particular word or letter using the Javascript Regex.
Sample strings would be:
// In the first 3 strings, I need "C" letter to be checked in the string
C is language is required.
We need a C language dev.
Looking for a dev who knows C!
// Keyword is Artificial Intelligence
We need looking for someone who knows Artificial Intelligence.
For checking the above I have created a Regex.
['C', 'Artificial Intelligence', 'D', 'Angular', 'JS'].forEach((item) => {
const baseRex = /[!,.?": ]?/g;
const finalRex = new RegExp(baseRex.source + item + baseRex.source); // /[!,.?": ]<C/D/Angular...>[!,.?": ]/
// Say checking for first iteration only. So let consider 'C'.
console.log(finalRex.test('C is required')); // true
console.log(finalRex.test('Looking for a dev who knows C!')); // true
console.log(finalRex.test('We need a C language dev.')); // true
console.log(finalRex.test('Computer needed')); // Also returns true | Which is wrong!
});
I won't want the words contains the letter C also get a count.
The regex after the concatenation with the baseRex is:
[!,.?": ]?C[!,.?": ]?
Notice that [!,.?": ]? can match 0 or 1 characters. In Computer, both subpatterns of [!,.?": ]? matches 0 characters, and C matches C, causing the whole regex to match.
Presumably, you added ? there so that it works at the start and end of the string, where there are no characters to be matched. However, you should instead use ^ and $ for the start and end instead. Your whole regex should be:
(?:[!,.?": ]|^)C(?:[!,.?": ]|$)
You can also replace the character class with \W, which means [^0-9a-zA-Z_].
In fact, you don't actually need to do all of this! There is a useful 0-width matcher called "word-boundary" \b, which seems to be exactly the thing you want here. Your base regex can just be:
\b
It only matches the boundary between a \w and a \W or between a \W and a \w.