The Wikimedia Foundation joined forces with Wikia to work on the project.[20] The implementation encountered challenges with the wiki markup language (the basis for Wikipedia articles), due to it being continuously extended over 12 years to include seldom-used rich and complex features making reproduction of the final article appearance dependent on many factors that were not easy to reproduce.[21] The technical implementation required improvements to MediaWiki in parsing, wiki markup language, the DOM and final HTML conversion.[22] A necessary component is a parser server called Parsoid[note 3] which is written in Node.js and was created to convert in both directions between wikitext and a format suitable for VisualEditor.[21] The Wikimedia Foundation considered VisualEditor its most challenging technical project to date.[4]