shouldComponentUpdate and componentWIllReceiveProps done well

updateIfPropsChanged.js

// @flow

import shallowEqual from "../shallowEqual";

type OnPropsChanged<Props> = (
  props: Props,
  component: React$Component<*, Props, *>
) => mixed;

const updateIfPropsChanged = <Props: Object, State: void | Object>(
  component: React$Component<*, Props, State>,
  onPropsChanged?: OnPropsChanged<Props>
) => {
  let propsChanged = false;

  const checkIfPropsChanged = props => {
    propsChanged = !shallowEqual(props, component.props);
  };

  const shouldComponentUpdate = (props: Props, state: State) => {
    if (state !== component.state) {
      return true;
    }

    if (!component.componentWillReceiveProps) {
      checkIfPropsChanged(props);
    }

    return propsChanged;
  };

  const componentWillReceiveProps = (props: Props) => {
    checkIfPropsChanged(props);

    // onPropsChanged can't never be undefined here (when it is, we are not
    // returning componentWillReceiveProps) but we need to check it as flow
    // is not detecting this fact
    if (propsChanged && onPropsChanged !== undefined) {
      onPropsChanged(props, component);
    }
  };

  return onPropsChanged !== undefined
    ? {componentWillReceiveProps, shouldComponentUpdate}
    : {shouldComponentUpdate};
};

export default updateIfPropsChanged;