Add link and examples for purecomponents

[lucas-aragno]

Discussed here: #8255 cc @lacker

[lucas-aragno]

Also I found some errors on the other page: #8478

[gaearon]

My overall feeling from this is it places too much emphasis on PureComponent and makes readers feel bad for not using it. This is not what we want to convey in this doc. We want people to know it exists and know basics of using it, but we only want them to use it when they have determined (with profiling) that it helps in a particular situation. Applying it blindly in some cases can make the app slower than it was.

Since Optimizing Performance already mentions PureComponent maybe it's worth changing it instead to include a separate heading (e.g. "Using React.PureComponent") . Then you can add a link from PureComponent reference to that section.

[lucas-aragno]

I see your point. I didn't get too well your last point, are you suggesting to remove the example and add a heading linking to optimising performance or move the example down to it's own heading ?

[sebmarkbage]

Changes requested above.

[notgiorgi]

@gaearon

Applying it blindly in some cases can make the app slower than it was.

How could this happen? I understand that, it might miss renders while data updates using mutations, but how === could be slower than deepEqual?

[bvaughn]

Thank you for submitting this PR! 😄

Unfortunately the documentation and source code for reactjs.org has been moved to a different repository: https://github.com/reactjs/reactjs.org

I realize this PR is old and there may no longer be interest in seeing it merged. If there is, please open a new PR there. Sorry for the inconvenience!

(For more backstory on why we moved to a new repo, see issue #11075)