twitter = usr => `twitter.com/${usr}`;

linkedin = usr => `linkedin.com/in/${usr}`;

github = usr => `github.com/${usr}`;

console.log(twitter('lmuller18'));
// https://twitter.com/lmuller18

console.log(linkedin('liammuller'));
// https://www.linkedin.com/in/liammuller/

console.log(github('lmuller18'));
// https://github.com/lmuller18