WhereforeArtThou.js

// Make a function that looks through an array of objects (first argument) and returns an array 
// of all objects that have matching name and value pairs (second argument). Each name and value 
// pair of the source object has to be present in the object from the collection if it is to be 
// included in the returned array.

// For example, if the first argument is [{ first: "Romeo", last: "Montague" }, { first: "Mercutio", last: null }, 
// { first: "Tybalt", last: "Capulet" }], and the second argument is { last: "Capulet" }, 
// then you must return the third object from the array (the first argument), because 
// it contains the name and its value, that was passed on as the second argument.

function whatIsInAName(collection,source){
    const sourceKeys = Object.keys(source);

    return collection.filter(obj => {
        for(let i = 0; i < sourceKeys.length; i++){
            if(obj[sourceKeys[i]] !== source[sourceKeys[i]]){
                return false;
            }
        }

        return true;
    })
}

console.log(whatIsInAName([{ first: "Romeo", last: "Montague" }, { first: "Mercutio", last: null }, { first: "Tybalt", last: "Capulet" }], { last: "Capulet" }));