JavaScript:
การใช้นิพจน์ปกติ

const str = "I love to code in JavaScript.";
const pattern = /code/;
const result = pattern.test(str);
console.log(result); // true

const matches = str.match(/code/);
console.log(matches[0]); // "code"
console.log(matches.index); // 10

const globalMatches = str.match(/o/g);
console.log(globalMatches); // ["o", "o", "o"]

const caseInsensitiveMatch = "JavaScript is fun".match(/javascript/i);
console.log(caseInsensitiveMatch[0]); // "JavaScript"

const newStr = "JavaScript is fun".replace(/fun/, "awesome");
console.log(newStr); // "JavaScript is awesome"

const groupedPattern = /(\w+) is (\w+)/;
const replaceWithGroups = "JavaScript is fun".replace(groupedPattern, "$2 is $1");
console.log(replaceWithGroups); // "fun is JavaScript"

// ตัวอย่างไลบรารี XRegExp
const XRegExp = require('xregexp');
const str = "Cats are fantastic.";
const unicodeWordMatch = XRegExp.match(str, XRegExp('\\p{L}+'), 'all');
console.log(unicodeWordMatch); // ["Cats", "are", "fantastic"]