5 expert ReactJS tips that you need to know today

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React has grown into one of the most popular tools found in a web developer’s library. Get yourself a selection of essential techniques that will improve your code output.

01. Higher-order components

Components often share functionality with each other, such as logging or network requests. These can become difficult to maintain as the number using this logic increases. Developers are encouraged to abstract shared code and include it where necessary. In a regular JavaScript application, the concept of a higher-order function is one way to approach it. In short, they are functions that take other functions as arguments and impart behaviours onto them. Array methods such as map and filter are examples of these. Higher-order components (HOCs) are React’s way of achieving the same thing. They are components that impart behaviour onto a passed component.

In this example here, the function returns a new wrapped component,
which renders the original one that was passed in alongside any props. HOCs are regular components and can do anything they can, such as passing in their own props and hooking into lifecycle callbacks. The function then wraps the original on export. By using HOCs, it makes commonly used chunks of code easier to maintain and test. When specific functionality is required, they are easy to drop in, safe in the knowledge that it will behave as expected.

02. Portals

There are times where a component needs to break out of its parent to be elsewhere in the DOM. Modal windows, for example, belong in the top level of the page in order to avoid issues with z-index and positioning.

Portals are also part in v16, which enables React to render components into DOM nodes completely separate from the rest of the application. The contents will keep its place in React’s structure, but will render elsewhere. This means any event that gets triggered inside the portal will bubble up through the parent in React, rather than into the portal container element itself.

By creating a dedicated component, the portal can be returned by the render function. When content needs to be displayed, it can be wrapped in this component and then displayed in the other element.

03. CSS with styled-components

Styling an application with reusable components can lead to issues with clashing class names. Conventions such as BEM help mitigate the issue, but they aim to treat the symptoms rather than the problem.

It is possible for components to take charge of their own styles. This means they have a way of adjusting visuals on the fly without the need for either inline styles or class toggles. One such solution is styled-components, which uses JavaScript to its advantage.

As the name suggests, rather than creating classNames it creates entirely new ready-styled components. The system makes use of ES2015 tagged template literals, which can accept regular CSS and apply that to the requested element.

By using a placeholder, the style can be altered dynamically. In this example, the button background changes depending if the button is passed a primary prop. Any expression can be used here to calculate the style required.

The created component can be used just like any other and any props will be passed through. Custom components can also be styled the same way by using styled(ComponentName) instead.

04. Using React-specific linting

One of the best ways to keep code clean is to use a linter tool. They define a set of rules the code should follow and will highlight anywhere it fails. By ensuring all code passes these rules before merging into the codebase, projects stay maintainable and code quality increases.

ESLint is a popular linter for various JavaScript projects. There are plugins available that analyse specific code styles. One of the most common for
React is an npm package called eslint-plugin-react.

By default, it will check a number of best practices, with rules checking things from keys in iterators to a complete set of prop types. More options can be enabled on a per-project basis by updating the .eslintrc config file.

Another popular plugin is eslint-plugin-jsx-a11y, which will help fix common issues with accessibility. As JSX offers slightly different syntax to regular HTML, issues with alt text and tabindex, for example, will not be picked up by regular plugins. It will also pick up React-specific issues, such as assigning aria props with different syntax.

05. Code splitting

As with any single page application, everything gets bundled into one file that can quickly bloom in size if it does not get kept in check. Tools such as Webpack can help split this bundle up into more manageable chunks that can then be requested as needed.

As React encourages creating lots of smaller components, there are plenty of opportunities to break up the bundle.
The react-loadable package enables a component to define exactly what it needs to render and Webpack can automatically split up its bundle to accommodate this.

Loadable is a HOC that will dynamically import anything the component needs. It takes a few settings, such as what to show while everything loads in, which makes it highly customisable. LoadableButton can then be used as a regular component without issue.

For larger applications with routing, it may be more beneficial to split by route instead of component. Common paths can be pulled in with one request, and can help speed things up. It is important to have a balance between the number of bundles and their overall size, which will change depending on the needs of the application.

More details about react-loadable can be found at https://github.com/thejameskyle/react-loadable.

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Wes Bos is a full-stack JavaScript developer, speaker and teacher from Canada. He works as an independent web developer, and is a lead instructor at HackerYou and Ladies Learning Code.

In his talk at Generate New York from 25-27 April 2018, he reveals some of the best things that are brand new to JavaScript, as well as things that we can look forward to in the coming months and years. Strap yourself in for a fast-paced talk full of hot tips as we rocket ourselves into the future of JavaScript. 

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