Solution to test question in form.

ranking.js

/**
 * Sort an array of objects based on ranking
 * @param {{name: String, ranking: Number}[]} objectArray 
 */
const sortByRanking = (objectArray) => {
    return objectArray.sort((obj1, obj2) => obj1.ranking-obj2.ranking);
};


/**
 * Find the average ranking of an array of objects.
 * Throws an exception if objectArray is empty
 * @param {{name: String, ranking: Number}[]} objectArray 
 */
const computeAverageRanking = (objectArray) => {
    if (objectArray.length) {
        const sumOfRanking = objectArray.reduce((prev, obj) => prev + obj.ranking, 0);
        const numOfObjects = objectArray.length;
        return sumOfRanking/numOfObjects;
    }
    throw new Error('objectArray param, must be non-empty');
};