sort and unique for lines from standard input.

sort+unique.js

function readStdinToLinsePromise() {
    return new Promise(function(resolve, reject) {
        const lines = [];
        const reader = require('readline').createInterface({
            input: process.stdin,
            output: process.stdout,
            terminal: false,
        });
        reader.on('line', function(line) {
            lines.push(line);
        });
        reader.on('close', function() {
            resolve(lines);
        });
        reader.on('error', function(error) {
            reject(error);
        });
    });
}

(async function () {
    if(process.stdin.isTTY) {
        // is terminal. (nop)
    } else {
        // is not terminal.
        let lines = await readStdinToLinsePromise();
        lines = [...lines].sort();
        lines = [...new Set(lines)];
        lines.forEach(function(line) {
            console.info(line);
        });
    }
})();