HTML onerror Attribute

Posted in HTML Tutorial

Updated on Jan 28, 2024

By Mari Selvan

👁️ 34 - Views

⏳ 4 mins

💬 1 Comment

Photo Credit to CodeToFun

🙋 Introduction

The onerror attribute is a powerful feature in HTML that allows developers to handle errors that may occur while loading an external resource, such as an image or a script.

This attribute is commonly used to provide fallback mechanisms or log errors when a resource fails to load.

🎯 Purpose of onerror

The primary purpose of the onerror attribute is to specify a JavaScript function to be executed when an error occurs during the loading of an external resource.

This enables developers to take specific actions, such as displaying an alternative image or logging the error for further analysis.

💎 Values

The onerror attribute accepts a JavaScript function as its value. This function will be triggered when an error occurs. Here's a simple example:

onerror.html

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<img src="example.jpg" onerror="handleError()">

🧠 How it Works

In this example, if the image with the source "example.jpg" fails to load, the handleError JavaScript function will be executed.

📄 Example

Let's look at a more comprehensive example of how to use the onerror attribute:

onerror.html

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<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>onerror Attribute Example</title>
  <script>
    function handleImageError() {
      console.log("Error loading image!");
      document.getElementById("fallbackImage").src = "fallback.jpg";
    }
  </script>
</head>
<body>
  <img src="example.jpg" onerror="handleImageError()" id="fallbackImage" alt="Fallback Image">
</body>
</html>

🧠 How it Works

In this example, if the image with the source "example.jpg" encounters an error, the handleImageError JavaScript function is called.

This function logs an error message and sets the source of an alternative image ("fallback.jpg") to provide a fallback.

🔄 Dynamic Values with JavaScript

You can dynamically set the onerror attribute using JavaScript, allowing for more flexibility in handling errors based on different conditions or user interactions:

onerror.html

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<script>
  // Dynamically set onerror for an image
  document.getElementById("dynamicImage").onerror = function() {
    console.log("Dynamic image loading error!");
    this.src = "dynamic-fallback.jpg";
  };
</script>

🧠 How it Works

In this script, the onerror attribute is dynamically set for an image with the id dynamicImage. If an error occurs while loading this image, a JavaScript function is executed to log an error message and set a dynamic fallback source.

🏆 Best Practices

Use the onerror attribute to gracefully handle errors and provide fallbacks for critical resources like images or scripts.
Ensure that the JavaScript function assigned to onerror is well-defined and handles errors appropriately.
Test your error-handling mechanisms across different browsers to ensure compatibility.