x.js

function createVideos() {
    // convert into tuples
    var primary = reduce(mocks.primary.videos, intoTupleList(3), [])
        , secondary = reduce(mocks.secondary.videos, intoTupleList(2), [])
        , random = mocks.random.videos

    // zip tuples together
    var zipped = zip([primary, secondary, random], concat)

    // flatten zipped tuples
    return concat.apply([], zipped)
}