How To Call Function From External Javascript File In Html

4 min read Jun 19, 2024

How To Call Function From External Javascript File In Html

How to Call Functions from External JavaScript Files in HTML

In web development, it's common practice to separate your HTML, CSS, and JavaScript code into distinct files for better organization and maintainability. This separation often involves calling functions defined in external JavaScript files from your HTML. Here's a breakdown of how to achieve this:

1. Create Your External JavaScript File

First, you'll need to create a separate JavaScript file to house your functions. Let's name it myFunctions.js.

// myFunctions.js
function greetUser(name) {
  alert("Hello, " + name + "!");
}

function calculateSum(num1, num2) {
  return num1 + num2;
}

2. Link the External File in Your HTML

In your HTML file, use the <script> tag to link the external JavaScript file. Place this tag within the <head> or <body> section of your HTML. It's generally recommended to place it before the closing </body> tag to ensure the script is loaded before the page is fully rendered.




  Calling External JavaScript

3. Calling Functions in HTML

Now you can call your functions from your HTML using the onclick event attribute or any other event handler.

Using onclick attribute:

Calling functions in JavaScript:

Explanation

src attribute: The src attribute in the <script> tag specifies the path to your external JavaScript file.
onclick attribute: The onclick attribute is attached to an HTML element (like a button) and calls a function when that element is clicked.

Best Practices

Consistent File Organization: Maintain a clear folder structure for your HTML, CSS, and JavaScript files. This makes your project more organized and easier to navigate.
Minimize Global Scope: Declare your functions within the global scope (outside any function blocks) only if they need to be accessible from anywhere in your code.
Use defer or async for better performance: The defer attribute instructs the browser to load the script after the HTML document has been parsed, improving the initial page load time. The async attribute allows the browser to load the script asynchronously, while the page continues parsing.

By following these steps and best practices, you'll be able to effectively leverage external JavaScript files to enhance the functionality and structure of your web pages.