Delving Deep into React: An In-Depth Look at React.createElement

4 min readMay 31, 2023

React is a widely-used JavaScript library for building user interfaces, primarily for single-page applications. It’s used for handling the view layer for web and mobile apps, allowing developers to create reusable UI components and react create element. React offers a declarative paradigm that makes it easier to reason about your application and aims to be both efficient and flexible. One of the fundamental concepts in React is the React.createElement method.

What is React.createElement?

React.createElement is a method provided by React which accepts several parameters and returns a new element of the specified type. In its simplest form, it is used as follows:

React.createElement(type, [props], [...children])

Type: The type argument can be either a tag name string (such as ‘div’ or ‘span’), a React component type (a class or a function), or a React fragment type.
Props: This optional argument is an object containing named properties (props) that get passed to the component. This can be anything from className, style, or any custom props.
Children: This is also an optional argument, which can be more React Elements that you want to nest inside the parent element.

A React Element is the smallest building block of a React app and it describes what you want to see on the screen. Not to be confused with browser DOM elements, React Elements are plain objects and are cheap to create.

Why Use React.createElement?

While React.createElement may seem verbose, it's extremely powerful. It's the base of JSX syntax which is more common and easier to write. The following JSX code:

<div className="App">
  <h1>Hello, World!</h1>
</div>

is actually syntactic sugar for:

React.createElement(
  "div",
  { className: "App" },
  React.createElement("h1", null, "Hello, World!")
)

Understanding the usage of React.createElement can give a better understanding of what happens under the hood when you write JSX.

The Role of Babel

Babel is a JavaScript compiler that takes your modern JavaScript code and returns browser compatible JavaScript. It translates JSX into React.createElement calls. This is one of the reasons why setting up a React environment requires a bit of configuration.

react element — Photo by Jefferson Santos

Working with React.createElement

Let’s take a closer look at how we can work with React.createElement by creating a simple React component.

const Hello = () => React.createElement('h1', null, 'Hello, World!');
ReactDOM.render(React.createElement(Hello, null, null), document.getElementById('root'));

In this example, we’ve created a function component called Hello that returns a React.createElement. The first argument is the HTML element type as a string ('h1'), the second is the props (we have none, so it's null), and the third is the children or the inner HTML.

React.createElement with Props

As we previously mentioned, React.createElement accepts props as its second argument. Let's see how we can pass a className to our component.

const Hello = () => React.createElement('h1', { className: 'greeting' }, 'Hello, World!');
ReactDOM.render(React.createElement(Hello, null, null), document.getElementById('root'));

In the above example, we passed an object as the second argument with a key of className and a value of ‘greeting’.

React.createElement with Children

We can also nest elements inside other elements by passing them as additional arguments to React.createElement.

const Hello = () => 
  React.createElement('div', { className: 'greeting' }, 
    React.createElement('h1', null, 'Hello, World!'),
    React.createElement('p', null, 'Welcome to our website.')
  );
ReactDOM.render(React.createElement(Hello, null, null), document.getElementById('root'));

Here, we’ve created a div with a className of ‘greeting’, and inside that div, we’ve added an h1 and a p element each with their own text.

React.createElement with Components

React.createElement can also create instances of React components. If you’ve created a class or function component, you can use it as the type argument in React.createElement.

class Hello extends React.Component {
  render() {
    return React.createElement('h1', null, 'Hello, World!');
  }
}

ReactDOM.render(React.createElement(Hello, null, null), document.getElementById('root'));

Here we’ve created a class component Hello that returns a React.createElement call. We then used Hello as the type argument when we called ReactDOM.render.

Conclusion

While most Reactjs developers will use JSX syntax to create their components and create element react, understanding React.createElement is key to understanding what happens behind the scenes. It's the function that JSX transpiles down to, and the function that actually creates your elements and components.

Becoming comfortable with React.createElement will give you a deeper understanding of React and help you become a more effective React developer. It's a fundamental part of the library and is crucial for anyone looking to understand more about the inner workings of React.

In the pursuit of mastering React, it might be beneficial to consider collaborating with an experienced team like CronJ IT Technologies. They offer competent React developers for hire, proficient in crafting high-quality, scalable web applications, with a deep understanding of the React ecosystem, including foundational concepts like React.createElement.

Happy coding!