Confusion about key.length === value.length about dataloader HOT 2 CLOSED

export const ArtistArticleIdsLoader = new DataLoader((ids) => new Promise((resolve, reject) => {
    DOQUERYTOGETARTICLEIDS.then((results) => {
        let res = results.map(result => result.id)
        resolve(res)
    )
}))

export const EventArticleIdsLoader = new DataLoader((ids) => new Promise((resolve, reject) => {
    DOQUERYTOGETARTICLEIDS.then((results) => {
        let res = results.map(result => result.id)
        resolve(res)
    )
}))

export const ArticleLoader = new DataLoader((ids) => new Promise((resolve, reject) => {
    DOQUERYTOGETARTICLES.then((results) => {
        resolve(results)
    )
}))

export default new GraphQLObjectType({
    name: 'Artist',
    fields: () => ({
                ...
                articles: {
                       type: new GraphQLList(ArticleType),
                       resolve: (artist, args, ast, { rootValue }) =>  {
                               return ArtistArticleIdsLoader.load(artist.id)
                              .then((articleIds) => {
                                      const promises = articleIds.map(id => ArticleLoader.load(id))
                                      return Promise.all(promises).then(results => results})
                              })
                       }
                }
        })
})