Conditional promises

_example.js

getArticles()
  .then(condition({
    if: (data) => data.length > 10,
    then: p => p
       .then(paginateArticles),
    else: p => p
       .then(sortArticles)
  })

condition.js

function condition (spec) {
  return function (value) {
    if (spec.if(value)) {
      return spec.then ? spec.then(Promise.resolve(value)) : value
    } else {
      return spec.else ? spec.else(Promise.resolve(value)) : value
    }
  }
}