[Javascript] Deep Search nested tag element in DOM tree

// For example you want to search for nested ul and ol in a DOM tree branch

// Give example <ol> <li> <ol> <li></li> </ol> </li> </ol> should retrun 2

function solution( tags = ['ul', 'ol']) {

const [uls, ols] = tags.map(tag => Array.from($(`${tag}`)));
const [logUl, logOl] = tags.map(tag => new Logger(`${tag}`));

deepSearch(uls, 'ul', logUl);
deepSearch(ols, 'ol', logOl);

return logUl.count + logOl.count;
}

class Logger {

    constructor(tag) {

        this.tag = tag;

        this.num = ;

    }

    get count () {

        return this.num;

    }

    get tagName () {

        return this.tag;

    }

    countOne() {

        this.num++;

    }

}

function deepSearch(els = [], tag = "", log) {

    // if no such elements passed in

    if (!els.length) {

        return;

    }

    log.countOne();

    // loop though the els and check whether contains tag

    els.forEach(el => {

        const targets = Array.from(el.getElementsByTagName(`${tag}`));

        if (targets.length) {

            deepSearch(targets, tag, log);

        }

    });

}