Part 4

4.0 Part 4 (clickable)

Child mounting

Going crazy, right? Let’s continue with investigating the mount method.

So, if _tag contains a ‘complex’ tag (1), like video, form, textarea, etc., it will require additional wrapping. It adds more event listeners for each media event, like ‘volumechange’ for audio tags, or it just wraps native behavior of tags like select, textarea, etc. There are a bunch of wrappers for elements like that, such as ReactDOMSelect and ReactDOMTextarea (inside src\renderers\dom\client\wrappers\ folder). In our case it’s just simply div, no additional processing there.

Props validation

The next validation method is called just to make sure that the internal props are set correctly, otherwise it will throw errors. For example, if props.dangerouslySetInnerHTML is set (usually we do that when try to insert HTML from a string) and object key __html is missed, the next error will be thrown:

props.dangerouslySetInnerHTML must be in the form {__html: ...}. Please visit for more information.

Create HTML element

Then, the actual HTML element will be created (3) by document.createElement, which will instantiate the real HTML div for us. Before we worked only with virtual representation and now, you can see it for the first time.

Alright, we’ve finished Part 4.

Let’s recap how we got here. Let’s look at the scheme one more time, then remove redundant less important pieces, and it becomes this:

4.1 Part 4 simplified (clickable)

And we should probably fix spaces and alignment as well:

4.2 Part 4 simplified & refactored (clickable)

Nice. In fact, that’s all that happens here. So, we can take the essential value from Part 4 and use it for the final mounting scheme:

4.3 Part 4 essential value (clickable)

And then we’re done!

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