Update index.js

[CosticaPuntaru]

https://reactjs.org/docs/react-component.html#setstate

react setState takes two parameters, updater and callback. As i think the api should respect the react api i suggest to add callback to the setState function.

[codecov]

Codecov Report

Merging #41 into master will decrease coverage by 0.87%.
The diff coverage is 66.66%.

@@            Coverage Diff             @@
##           master      #41      +/-   ##
==========================================
- Coverage   96.11%   95.23%   -0.88%     
==========================================
  Files           1        1              
  Lines         103      105       +2     
  Branches       31       32       +1     
==========================================
+ Hits           99      100       +1     
- Misses          4        5       +1

Impacted Files	Coverage Δ
src/index.js	95.23% <66.66%> (-0.88%)	⬇️

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[ctrlplusb]

Hey @CosticaPuntaru

Thanks for raising this.

Hmmm, interesting. Is it expected for the callbacks to be executed synchronously in a server rendering context? What is the default React behaviour around this?