Flexbox polyfill for IE8 and IE9

Today, 10up has made public a polyfill I knew they were working on, and was begging for: Flexibility. Flexibility provides IE8 and IE9 Flexbox compatibility.

For those of you (like me) that still like to support IE9 — and the wild out there often support IE8 too — this is a good day.

Flexbox is a great tool, but without at least some older IE support, it's often a non-starter other than for the most trivial of layout components. Now, you can use Flexbox pretty sitewide, thanks to 10up's efforts.
Using Flexibility is as easy as putting an extra -js-display property in your Flexbox CSS.

Fair warning, they do say it's incomplete:

While Flexibility is still in active development, it can already do so much. Therefore, it has been released even in an incomplete state.

But I imagine for most of us, it's in pretty good shape as is, even if it doesn't have 100% Flexbox coverage.

Like they say on the Github page, you should definitely read Chris Coyier's complete guide to Flexbox if you haven't already.