Note from the publisher: You have managed to find some of our old content and it may be outdated and/or incorrect. Try searching in our docs or on the blog for current information.
To learn more about how to install Yarn in your CircleCI builds–including a full example–read more in our documentation.
Yarn was a the result of a collaboration between Google, Facebook, Exponent and Tilde and was released in October 2016. To learn more about Yarn in general, you can check out their repo or the announcement on Facebook.