[ChrisCinelli]

One thing that has been bothering me is that React is slow by default. It re-renders everything every time unless you start looking into shouldComponentUpdate.

Even if I agree that premature optimization is the root of all evils, I like when the language and the framework I use make it writing fast code as easy as writing slow code.

I wonder if anybody has evaluated, the improvement they get in development speed using React when they add the time they have to spend to optimizing their React code.

In my experience, I am not even frustrated with React itself most of the time but with the other things in the ecosystem.

[dounan]

In our experience, React is not necessarily 'slow' by default. Re-constructing parts of the element tree each time can be a bit wasteful, but it is only as slow as your render() methods, and that is outside of React's control.

We have survived over 3 years with a massive application (over 2000 modules) and tons of wasteful re-rendering, but have only now started to notice any sluggishness. That makes React pretty fast in my mind.

Having said all that, we are experimenting with an 'all PureComponents' approach to potentially make React, but whether that turns out to be a good idea is yet to be seen (object comparisons in sCU are not free).

[seangrogg]

Hmm, my experience has been pretty much the opposite. Even without optimization, React's renders won't cause a DOM update unless there is something to diff - I can't say the same for jQuery or Angular 1.x. As well, being big on the "don't use it unless you need it" bandwagon I tend to wait until I see components and re-use in my code before I import React in the first place.

If the total re-render is occurring under 16.67ms (60fps) in a non-trivial use-case I'm usually fine leaving it as-is. Most render cycles taking longer than that involve operations on large data sets or events firing at the millisecond level (mouseover, drag, etc) - and those are worth fixing as they'll actually have noticeable impacts on the user experience. But I tend not to optimize just to pat myself on the back for "optimization".