/*
Normalize a string:
- Convert letters to lowercase
- Replace any non-letter with a space
This ensures consistent word comparison.
*/
function normalize(text) {
let result = "";
for (const ch of text) {
if (/[a-zA-Z]/.test(ch)) {
result += ch.toLowerCase();
} else {
result += " ";
}
}
return result;
}
/*
Extract words from a string.
This function:
- Normalizes the input
- Splits on whitespace
- Filters out empty entries
- Returns a Set for fast lookup and automatic duplicate removal
*/
function extractWords(text) {
const normalized = normalize(text);
const parts = normalized.split(/\s+/);
const words = new Set();
for (const w of parts) {
if (w.length > 0) {
words.add(w);
}
}
return words;
}
/*
Find common words between two strings.
This function:
- Extracts words from both strings
- Uses set intersection for efficiency
- Returns a new Set containing the common words
*/
function findCommonWords(a, b) {
const wordsA = extractWords(a);
const wordsB = extractWords(b);
const common = new Set();
for (const w of wordsA) {
if (wordsB.has(w)) {
common.add(w);
}
}
return common;
}
/*
Main execution
*/
const s1 = "The quick brown fox jumps over the lazy dog.";
const s2 = "A lazy dog sleeps while the quick fox runs away.";
const common = findCommonWords(s1, s2);
console.log("Common words:");
for (const w of common) {
console.log(w);
}
/*
run:
Common words:
the
quick
fox
lazy
dog
*/
