Polyfill: for the gap between theory and reality

Today was a fun day hopping from one educational site to another. Since I just completed the jQuery track on Codecademy, I thought I’d look around for additional jQuery resources before I dive into another Codecademy track. The jQuery Learning Center sent me to the Mozilla Developer Network which in turn sent me to Google Developer resources which set me to…

Every one of those sites would occasionally mention some kind of polyfill. It’s not the first time I came across the term, but I had assumed it was a vector graphics concept: Draw a polygon and fill it with a color, or something along those lines. As I came across more and more polyfill references, though, I started to realize my original assumption was wrong.

In the current web development world, there’s the grand theory of HTML5, the gold standard by which all of the web will flourish. But in the real world, we are hampered by the fact that none of the browsers fully implement web standards in all the same ways. There’s even a web site set up to document all the ways in which various browsers fail to fully implement these standards.

The gap between theory and reality is bridged by polyfill, a category of tools created by various frustrated developers to make individual real-world web browsers work closer to somebody’s idea of perfect browser.

Coming from the world of operating system development, I know of this concept by the name of “compatibility shims” and I’ve even had the misfortune privilege of writing a few of them myself. Since they’re bridging the ideal world and the ugliness of the real world, shims are never great pieces of code. A shim is always constrained by some inconvenient reality, written to solve a very specific problem, and never quite live up to the ideal.

So I was not terribly surprised that we have many, many polyfill libraries floating around. Each can solve a specific problem under a specific circumstance, none are capable of solving all the problems perfectly. To solve a specific problem, a developer would have to comb through the list and test to figure out which polyfill to use. I’m sure some end up writing a quick-and-dirty solution to their one Problem of the Day instead of using a library.

But I do admire the ideal of having a centralized resource!

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