2618. Check if Object Instance of Class

/**
 * @param {any} obj
 * @param {any} classFunction
 * @return {boolean}
 */
var checkIfInstanceOf = function(obj, classFunction) {
    const prototype = classFunction?.prototype;
    while (obj !== null && obj !== undefined) {
        obj = Object.getPrototypeOf(obj)
        if (obj === prototype) return true;
    }
    return false;
};

/**
 * checkIfInstanceOf(new Date(), Date); // true
 */