k-nearest neighbors in js

kNearestNeighbors.js

function findMetrics(values) {
    return Math.hypot(...values);
}

export function updateWithMetrics(usersVotes) {
    if (obj(usersVotes).doesntExist()) return null;

    for (let i = 0, len = usersVotes.length; i < len; i++) {
        const currentUser = usersVotes[i];

        if (currentUser['metrics']) continue;
        else usersVotes[i]['metrics'] = findMetrics(currentUser['votes']);
    }
}

export function kNearestNeighbors(usersVotes, target, amount) {
    if (obj(target).doesntExist() || obj(usersVotes).doesntExist()) return null;
    if (someKeys('votes', 'name', 'id').dontExistIn(target)) return null;

    let biggestDistanceInStack = Infinity;
    let smallestDistanceInStack = 0;
    let stackOfNeighbors = [];
    for (let i = 0, len = usersVotes.length; i < len; i++) {
        const currentUser = usersVotes[i];
        if (currentUser['id'] === target['id']) continue;
        const distanceBetweenTargetAndCurrentUser = Math.abs(target['metrics'] - currentUser['metrics']);
        if (typeof(stackOfNeighbors[0]) === "undefined") {
            stackOfNeighbors.push(currentUser);
            smallestDistanceInStack = distanceBetweenTargetAndCurrentUser;
            continue;
        }
        if (typeof(stackOfNeighbors[amount - 1]) === "undefined") {
            stackOfNeighbors.push(currentUser);
            if (distanceBetweenTargetAndCurrentUser < biggestDistanceInStack 
                && distanceBetweenTargetAndCurrentUser > smallestDistanceInStack) {
                biggestDistanceInStack = distanceBetweenTargetAndCurrentUser;
            } else if (distanceBetweenTargetAndCurrentUser < smallestDistanceInStack) {
                if (biggestDistanceInStack === Infinity) biggestDistanceInStack = distanceBetweenTargetAndCurrentUser;
                smallestDistanceInStack = distanceBetweenTargetAndCurrentUser;
            }

            continue;
        }

        stackOfNeighbors.sort((a,b) => {
            return Math.abs(target['metrics'] - a['metrics']) - Math.abs(target['metrics'] - b['metrics']);
        })

        if (distanceBetweenTargetAndCurrentUser < biggestDistanceInStack 
            && distanceBetweenTargetAndCurrentUser > smallestDistanceInStack) {
                biggestDistanceInStack = distanceBetweenTargetAndCurrentUser;
                stackOfNeighbors.pop();
                stackOfNeighbors.push(currentUser);
        } else if (distanceBetweenTargetAndCurrentUser < smallestDistanceInStack) {
            if (biggestDistanceInStack === Infinity) biggestDistanceInStack = distanceBetweenTargetAndCurrentUser;
            smallestDistanceInStack = distanceBetweenTargetAndCurrentUser;
            stackOfNeighbors.shift();
            stackOfNeighbors.push(currentUser);
        } else if (distanceBetweenTargetAndCurrentUser < biggestDistanceInStack) {
            stackOfNeighbors.pop();
            stackOfNeighbors.push(currentUser);
            biggestDistanceInStack = distanceBetweenTargetAndCurrentUser;
        }
    }

    return stackOfNeighbors;
}

function someKeys(...objKeys) {
    return {
        dontExistIn(obj) {
            for (let i = 0, len = objKeys.length; i < len; i++) {
                if (!obj[objKeys[i]]) return true;
            }
        }
    }
}

function obj(objName) {
    return {
        doesntExist() {
            return typeof objName !== "object";
        }
    }
}

// Example of usage
// const usersVotes = [
//     {
//         votes: [0, 0, 5, 5, 3],
//         name: 'Michael',
//         id: 0
//     },
//     {
//         votes: [1, 1, 1, 1, 1],
//         name: 'Ulf',
//         id: 1
//     },
//     {
//         votes: [5, 5, 5, 5, 5],
//         name: 'Juliette',
//         id: 2
//     },
//     {
//         votes: [2, 3, 1, 5, 2],
//         name: 'Aurelie',
//         id: 3
//     },
//     {
//         votes: [4, 4, 0, 4, 5],
//         name: 'Aleksandr',
//         id: 4
//     },
//     {
//         votes: [1, 2, 3, 4, 5],
//         name: 'Un Garson',
//         id: 5
//     },
//     {
//         votes: [5, 4, 3, 0, 0],
//         name: 'Justin',
//         id: 6
//     },
//     {
//         votes: [1, 1, 2, 4, 5],
//         name: 'Jean-Noel',
//         id: 7
//     },
//     {
//         votes: [1, 0, 3, 4, 0],
//         name: 'Ekaterina',
//         id: 8
//     },
//     {
//         votes: [1, 0, 0, 4, 0],
//         name: 'Evgeniy',
//         id: 9
//     },
//     {
//         votes: [1, 0, 3, 4, 0],
//         name: 'Igor',
//         id: 10
//     }
// ]

// updateWithMetrics(usersVotes);
// console.log(kNearestNeighbors(usersVotes, usersVotes[5], 3));