Composing Web Components

Thu Apr 26, 2018

Last week I was attempting to build a searchable dropdown box using Polymer. I knew that composability was important and decided to pull in [iron-input]() and [iron-dropdown]() and started coding the two pieces together. I managed to coble something together but it was pretty rough and required looking for all sorts of edge cases. I pulled in one of our other Polymer devs and found out about a few more components that we have published.

First up was d2l-hierarchical-view which seemed completely unrelated to a searchable dropdown. That component is used by d2l-menu which again, seems a bit different from what I was making. That’s when I discovered d2l-dropdown which makes use of menu (sometimes) and is very open to extension. Combine that with d2l-text-input as the trigger for the dropdown and now we’re looking great.

In the end, we’re using the hierarchical-view component through all those other components and the dropdown menu fires events off to whomever uses the component to decide what to do. If you have the full list of options in the dropdown then you can just filter. If you want to support paging or server side searching, you can do that too.

When we end up publishing it, it’ll be in d2l-dropdown and the component will be called d2l-dropdown-input. It won’t be terribly exciting though. It’s 2 lines of template and very few lines of JavaScript. All the work is being done by the other web components. Exciting times we live in.

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