Twitter’s widgets-js script throws an error if the website uses FastDOM 1.0:
widgets.js:8 Uncaught (in promise) TypeError: u.write is not a function(…)
JSFiddle demo: https://jsfiddle.net/steffenweber/bph95z8j/
Twitter’s widgets-js checks whether
window.fastdom exists. If it does not exist then widgets-js injects its own copy of FastDOM 0.x and everything is fine. However, if
window.fastdom does exist then widgets-js uses it assuming that the FastDOM version is 0.x and not the current version 1.0 (which has a completely different API). This is where things break.
fastdom.write have been renamed to
fastdom.mutate in FastDOM 1.0. Furthermore,
fastdom.defer has been removed.