Practical Guide to Conditional Rendering in JavaScript

Conditional rendering is a powerful technique in web development, allowing you to dynamically display content based on certain conditions. This approach can significantly enhance the user experience by showing relevant information and hiding unnecessary details.

Conditional Rendering in Vanilla JavaScript

In vanilla JavaScript, conditional rendering can be achieved through direct manipulation of the DOM based on your application’s state or user interactions.

I. Example: Displaying a Message Based on User Input

// HTML structure
<div id="greeting"></div>
<input type="text" id="username" placeholder="Enter your name">
<button onclick="showGreeting()">Submit</button>

// JavaScript
function showGreeting() {
  const username = document.getElementById('username').value;
  const greeting = document.getElementById('greeting');

  if (username) {
    greeting.textContent = `Hello, ${username}!`;
  } else {
    greeting.textContent = 'Hello, guest!';

This example checks if the user has entered a name. Based on this condition, it dynamically updates the content of the greeting div.

II. Techniques for Dynamic Content Display

  1. Using if-else Statements: The most straightforward method for conditional rendering.
  2. Manipulating CSS Classes: Toggle visibility of elements by adding or removing CSS classes.
  3. Creating and Removing Elements: Programmatically add or remove elements from the DOM based on conditions.

Conditional Rendering in JavaScript Frameworks

Frameworks like React, Angular, and Vue offer more streamlined approaches to conditional rendering, often through template syntax or specific directives.

I. React Example: Conditional Rendering

React allows conditional rendering within the JSX template by using JavaScript expressions.

function WelcomeMessage({ username }) {
  return (
      {username ? (
        <h1>Hello, {username}!</h1>
      ) : (
        <h1>Hello, guest!</h1>

This component displays a personalized greeting if username is provided; otherwise, it defaults to greeting a guest.

II. Angular Example: Using the *ngIf Directive

Angular provides structural directives like *ngIf for conditional rendering within templates.

<!-- Angular template -->
<h1 *ngIf="username; else guestTemplate">Hello, {{ username }}!</h1>
<ng-template #guestTemplate><h1>Hello, guest!</h1></ng-template>

The *ngIf directive checks if username exists, displaying the appropriate greeting based on the condition.

III. Vue Example: The v-if Directive

Vue uses the v-if directive for conditional rendering within its templates.

<!-- Vue template -->
<h1 v-if="username">Hello, {{ username }}!</h1>
<h1 v-else>Hello, guest!</h1>

The v-if and v-else directives toggle the display of elements based on the truthiness of username.


Conditional rendering is essential for creating dynamic web applications that respond to user input and application state. Whether you’re working with vanilla JavaScript or using a framework, understanding and implementing conditional rendering techniques can greatly improve the interactivity and user experience of your web applications.