Question
Answer and Explanation
To create a regular expression (regex) that matches all words where a specific letter appears exactly twice, you can employ capturing groups and backreferences. Here's how:
Let's consider that your specific letter is 'a'.
The regex pattern you'd use is: \b\wa\wa\w\b
Here's a breakdown of this pattern:
\b: This matches a word boundary, ensuring that we're matching whole words and not partial ones.\w: This matches zero or more word characters (alphanumeric characters and underscores), which could appear before the first occurrence of 'a'.a: This matches the specific letter, in our example 'a'.\w: This matches zero or more word characters that appear after the first 'a', and before the second 'a'.a: This matches the second occurrence of the specific letter, which is 'a'.\w: This matches zero or more word characters that appear after the second 'a'.\b: Another word boundary to ensure the entire word is matched.To apply this regex in JavaScript, you can do something like this:
const text = "banana apple aardvark amazing data";
const regex = /\b\wa\wa\w\b/g;
const matches = text.match(regex);
console.log(matches); // Output: ["banana", "data"]
If you want to make it work with a dynamic letter, you can create a function. Let's call it findWordsWithLetterTwice:
function findWordsWithLetterTwice(text, letter) {
const regex = new RegExp(`\\b\\w${letter}\\w${letter}\\w\\b`, 'g');
const matches = text.match(regex);
return matches || [];
}
const text = "hello balloon umbrella success";
const letter = "l";
const result = findWordsWithLetterTwice(text, letter);
console.log(result); // Output: ["hello", "balloon"]
This approach makes the regex adaptable to search for any letter appearing exactly twice within words. The key idea is to use the word boundary \b and the wildcard \w to create a versatile pattern that captures only the full words meeting the criteria.