HOC Cheatsheet

This HOC Cheatsheet compiles all available knowledge for writing Higher Order Components with React and TypeScript.

• We will map closely to the official docs on HOCs initially
• While hooks exist, many libraries and codebases still have a need to type HOCs.
• Render props may be considered in the future
• The goal is to write HOCs that offer type safety while not getting in the way.

There are a lot of use cases where an HOC is used. For example:

• HOCs can wrap components to check if a user is authenticated before rendering, or to restrict access based on user roles.
• An HOC can conditionally render components based on feature flags or A/B testing.
• An HOC can provide translation functionality to components.
• An HOC can add logging or analytics tracking to components without modifying their core logic.

Here is a base HOC example you can copy right away:

type PropsAreEqual<P> = (
  prevProps: Readonly<P>,
  nextProps: Readonly<P>
) => boolean;

const withSampleHoC = <P extends {}>(
  component: {
    (props: P): Exclude<React.ReactNode, undefined>;
    displayName?: string;
  },
  propsAreEqual?: PropsAreEqual<P> | false,

  componentName = component.displayName ?? component.name
): {
  (props: P): React.JSX.Element;
  displayName: string;
} => {

  function WithSampleHoc(props: P) {
    //Do something special to justify the HoC.
    return component(props) as React.JSX.Element;
  }

  WithSampleHoc.displayName = `withSampleHoC(${componentName})`;

  let wrappedComponent = propsAreEqual === false ? WithSampleHoc : React.memo(WithSampleHoc, propsAreEqual);

  //copyStaticProperties(component, wrappedComponent);

  return wrappedComponent as typeof WithSampleHoc
};

This code meets these criteria:

1. Allows a component to return valid elements (strings | array | boolean | null | number) and not just React.JSX.Element | null.
2. Wraps it in a memo unless you opt out.
3. Removes the nested component, so React Dev tools will just show one component.
4. Indicates with displayName in React Dev Tool with an annotation that this is a component wrapped in two HoCs
5. Optional: Copies over static properties that might have been defined on the original component.