为什么以及Object.assign如何提高React中的应用程序性能？

Question

I am reading the Facebook tutorial for React . About 40% of the way through, there's a section called Why Immutability is Important where they state (regarding the importance of immutability):

The end result is the same but by not mutating (or changing the underlying data) directly we now have an added benefit that can help us increase component and overall application performance .

My question is: why/how? That is, in React, specifically why/how does immutability (using Object.assign(...) , etc.) "help increase...overall application performance"?

Answer 1

I think that it is easier to understand with arrays :

Imagine that you have an array , containing many, many entries. You replace one entry with another - to see if anything changed react has to loop through the whole array .

Now, imagine that everytime you make some changes you create new array - then the only thing react has to do is to compare references

Object.assign does the same - instead of changing existing object , you create a new one, so that react can detect changes simply by comparing references