How JSX variables work in React

  • React
  • Gabriele Romanato

JSX is a syntax extension for JavaScript that allows developers to write HTML-like code directly in their JavaScript code. One of the fundamental concepts in JSX is the use of variables, which enable developers to dynamically change the content and appearance of their JSX elements. In this article, we will explore how variables work in JSX.

JSX variables can be declared using the curly braces syntax { }, which indicates that the value inside the braces should be treated as a JavaScript expression. For example, if we want to display a dynamic message based on a variable, we can use the following code: 


const message = 'Hello, world!';
const element = <h1>{message}</h1>;

In this example, the variable message is declared with the value "Hello, world!". We then create a JSX element using the h1 tag and wrap the message variable in curly braces inside the element's content. When the code is executed, the variable's value is inserted into the element, and the resulting HTML looks like this:


<h1>Hello, world!</h1>

JSX variables can also be used to control the appearance of elements. For example, we can set the style of an element based on a variable like this:


const style = {
    color: 'red',
    fontSize: '20px'
};
const element = <h1 style={style}>Hello, world!</h1>;

In this example, we declare a variable style that contains an object with CSS properties as key-value pairs. We then create a JSX element using the h1 tag and pass the style variable as a prop using the style attribute. When the code is executed, the element's style is set to the values defined in the style variable.

JSX variables can also be used in conditional statements and loops to dynamically generate elements. For example, we can use the map() method to create a list of elements based on an array of data:


const items = ['apple', 'banana', 'cherry'];
const list = (
    <ul>
        {items.map((item) => (
            <li key={item}>{item}</li>
        ))}
    </ul>
);

In this example, we declare an array items with three string values. We then create a JSX element using the ul tag and use the map() method to iterate over the items array and create a list of li elements with the item value as their content. The key attribute is used to ensure each item in the list has a unique identifier.

In conclusion, variables are a powerful tool in JSX that enable developers to dynamically change the content and appearance of their elements. By using variables in conjunction with other JavaScript features like conditional statements and loops, developers can create dynamic and responsive UIs with ease.

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