Pros and cons of using react's life cycle methods in arrow function format

Question

I'm using the public class field syntax (handler = () => {...}) to define all my React components' event handlers so that I can use this for my components without binding them in the constructor. I'm wondering can I use this syntax to use React life cycle methods as well? Say use componentWillMount in this way: componentWillMount = () => {...}

What are the pros and cons if defining react's life cycle method with arrow functions?

Answer 1

Each time your function performs a => operation it has to create a new function object. This prevents the browser from reusing the same function when rendering multiple copies of the same element which makes optimization by the javascript engine harder to do. This would cause performance issues(, but in most programs, it won't be noticeable).

It is recommended not to use arrow functions for life-cycle methods in React

When should you use arrow functions

Answer 2

There shouldn't be a need in component lifecycle methods to implicitly bind this (ie: use arrow functions). They are always called from the context of the component, so access to props, state, getState, etc are already available.

So there are no advantages to this pattern. Some disadvantages I can think of are:

1. More verbose syntax that is still just an ECMAScript proposal.
2. Confusing to other collaborators. If you are binding this on a component method, I immediately expect that is going to be called by some other entity downstream, ie: click event handlers passed from parent to child.