function cleanUniqueDocument(request) {
return arr = [], elements = [], Promise.all(request.map( async (e) => {
return elements.map(function(i) { return i.tags }).indexOf(e.tags.join()) < 0 && elements.push({
href: e.url,
tags: e.tags.join()
}) || (e.canonical = elements.find(x => x.tags === e.tags.join()).href) && arr.push(e)
}))
.then(e => {
return arr || []
})
}