Deep object access by string path

frontend.js

// This function can be used on frontend. For better performance use the "for" version

Object.byString = function(object, string) {
    string = string.replace(/\[(\w+)]/g, '.$1'); // convert indexes to properties
    string = string.replace(/^\./, ''); // strip a leading dot
    const array = string.split('.');
    array.forEach((key) => {
        if (key in object) object = object[key];
    });
    return object;
}

node.js

// Better performance, suggested to use in node

Object.byString = function(object, string) {
    string = string.replace(/\[(\w+)]/g, '.$1'); // convert indexes to properties
    string = string.replace(/^\./, ''); // strip a leading dot
    const array = string.split('.');
    for (let index = 0, limit = array.length; index < limit; ++index) {
        const key = array[index];
        if (key in object) {
            object = object[key];
        } else {
            return;
        }
    }
    return object;
}

Difference of performance here: https://jsbench.me/p6kpx0bqgh/1

Thanks to Alnitak, to post the solution.