Install

npm i --save @uplab/should-update

Intro

There is a time when a React Developer evolves to a Good React developer and decides to add shouldComponentUpdate to every component that cannot be PureComponent. In most cases ones shouldComponentUpdate function implementation looks similar to this:

class DeathStar extends Component {
  shouldComponentUpdate(nextProps) {
    return (
      this.props.jedi.id !== nextProps.jedi.id ||
      this.props.jedi.name !== nextProps.jedi.name ||
      this.props.jedi.profile.firstName !== nextProps.jedi.profile.lastName
      // ... forevermore 
    );
  }
}

Solution

This package is made to simplify the API for props and state comparison to a single function call. @uplab/should-update can deal with nested properties and accepts an array on dependencies that are presented as a path string (i.e. some.very.deeply.nested.data.and.even.array[0].items). It can track not only the props change, but a state changes.

Example usage:

import { createShouldUpdate } from '@uplab/should-update';

class DeathStar extends Component {
  state = {
    formState: {
      firstName: 'Anakin',
      lastName: 'Skywalker',
    }
  }
  shouldComponentUpdate: createShouldUpdate({
    dependencies: ['jedi.id', 'jedi.name', 'jedi.profile.firstName'],
    stateDependencies: ['formState'],
  })
}

or

import { shouldUpdate } from '@uplab/should-update';

class DeathStar extends Component {
  state = {
    formState: {
      firstName: 'Anakin',
      lastName: 'Skywalker',
    }
  }

  shouldComponentUpdate(nextProps, nextState) {
    const dataChanged = shouldUpdate({
      dependencies: ['jedi.id', 'jedi.name', 'jedi.profile.firstName'],
      stateDependencies: ['formState'],
      state: this.state,
      props: this.props,
      nextProps,
      nextState,
    });
    // some custom stuff with dataChanged
  }
}

By default, if the resolved path is a type of object, then the deep comparison happens to check all the nested props. To avoid this behavior when you have complex and huge objects you can pass shallow: true prop:

shouldComponentUpdate: createShouldUpdate({ dependencies: ['jedi.profile'], shallow: true, stateDependencies: ['formState'] })

or

shouldUpdate({
  dependencies: ['jedi.profile'],
  props: this.props,
  nextProps,
  shallow: true, //defaults to false
  stateDependencies: ['formState'],
  state: this.state,
  nextState,
});

API

shouldUpdate(params)

• @param {array} params.dependencies - array of pathes of the properties to depend on
• @param {object} params.props - component props
• @param {object} params.nextProps - component changed props. Can be previous or next props
• @param {boolean} [params.shallow = false] - if true then the function will do shallow comparison.
• @param {array} params.stateDependencies - array of pathes of the properties to depend on
• @param {object} params.state - component state
• @param {object} params.nextState - component changed state. Can be previous or next state

Returns true if the component should update, else false.

createShouldUpdate(params)

Same as shouldUpdate, but without params.props and params.nextProps