test.js

class EfficientPrinter {

    constructor() {

        this.lines = null;

    }

    render(text) {

        let buffer = ``;

        let oldLines = this.lines || [];
        let newLines = String(text).split(/\n/g);

        this.lines = newLines;

        for (let y = 0; y < newLines.length; ++y)
            if (y < newLines.length && newLines[y] !== oldLines[y])
                buffer += `\x1b[${1+y};1H\x1b[K${newLines[y]}`;

        if (newLines.length < oldLines.length)
            buffer += `\x1b[${1+newLines.length};1H\x1b[J`;

        process.stdout.write(buffer);

    }

}

// -- demo

let lines = [];

for (let t = 0; t < process.stdout.rows; ++t)
    lines[t] = randomLine();

let printer = new EfficientPrinter();

function randomLine() {
    return require('crypto').randomBytes(50).toString('hex');
}

setInterval(() => {
    lines[Math.floor(Math.random() * lines.length)] = randomLine();
    printer.render(lines.join(`\n`));
}, 1000 / 60);