This is how to use jsdom repetitively without leaking memory

test2.js

const jsdom = require('jsdom');

const domBuilder = (iter) => {
    new jsdom.JSDOM(`${iter}`);

    if (iter % 1000 === 0) {
        console.log(iter);  // eslint-disable-line no-console
    }

    setImmediate(domBuilder.bind(null, iter + 1));
};

domBuilder(0);

This kind of thing occurs because jsdom silently schedules some procedure for a generated Window object at the next tick.
Therefore, calling JSDOM() multiple times within a single tick, like this, leaves heavy Window objects referenced from the task queue of Node.js and results in heap depletion eventually.