react-update-checker

Console warnings for when a React component updates even though the props/state are deeply equal.

Install

$ npm install react-update-checker

Usage

For components that extend React.PureComponent, simply change the parent class to ReactUpdateChecker instead.

import ReactUpdateChecker from 'react-update-checker';

- class MyComponent extends React.PureComponent { }
+ class MyComponent extends ReactUpdateChecker { }

The above also works for components extending React.Component but do not implement a shouldComponentUpdate method.

If your component does have a shouldComponentUpdate method, extend the ReactUpdateChecker class and call the super method as the first statement in your shouldComponentUpdate

import ReactUpdateChecker from 'react-update-checker';

- class MyComponent extends React.Component {
+ class MyComponent extends ReactUpdateChecker {

    shouldComponentUpdate(newProps, newState) {
+     super.shouldComponentUpdate(newProps, newState);

      // existing shouldComponentUpdate logic here
    }
}

API

When process.env.NODE_ENV === 'production', the default export of this package will simply be React.PureComponent. This prevents blasting the console messages unexpectedly in a production environment.

ReactUpdateChecker

import { ReactUpdateChecker } from 'react-update-checker';

class MyComponent extends ReactUpdateChecker {}

The named export is identical to the default export, except it always returns the custom class, regardless of process.env.NODE_ENV.

getFailedKeys(object1, object2)

import { getFailedKeys } from 'react-update-checker';

const sameReference = {};

const oldProps = {
  id: 'some-id',
  letters: ['a', 'b', 'c'],
  obj: sameReference
};

const newProps = {
  letters: ['a', 'b', 'c'],
  obj: sameReference
};

getFailedKeys(oldProps, newProps);
// => ['letters']

Given 2 objects, returns a list of property keys where the corresponding values are deeply equal but not shallowly equal. These are typically the prop/state items that need to be adjusted to avoid a re-render. Note that this only checks properties that are common between both objects. Any new or removed properties are not included in the return value.

isShallowEqual(object1, object2)

import { isShallowEqual } from 'react-update-checker';

isShallowEqual({ foo: 'bar' }, { foo: 'bar' });
// => true

Given 2 objects, returns whether or not all top-level properties are equal. This is the exact same shallow comparison that is done by React.PureComponent, just re-exported in this module for convenience.

What about why-did-you-update?

You should probably just use that project instead. I originally needed something more targeted (no monkey-patching React) and needed it to be painfully obvious which prop/state names were causing the problem.

License

MIT