Selecting HTML elements by their href attribute value is a common task in JavaScript web development. This guide will explore a variety of methods, real-world applications, and best practices for robust href attribute selection.
Typical Web Development Use Cases
Before diving into the technical details, let‘s look at some practical examples of why getting elements by href is useful:
Building Browser Extensions
Browser extensions often monitor clicks on links and process the href values. For example:
- An ad blocker checks if a clicked link points to a known ad provider and blocks the request.
- A URL shortener extension expands shortened links when clicked to reveal the destination.
Here is sample code from a hypothetical browser extension:
// Listen for clicks on anchor elements
document.addEventListener(‘click‘, e => {
// Get the clicked element
const clickedEl = e.target;
// Check if it is an anchor tag
if (clickedEl.tagName === ‘A‘) {
// Get its href value
const href = clickedEl.getAttribute(‘href‘);
// Extension logic with href value
}
});Web Scrapers
Web scrapers extract data from websites through automated JavaScript. Getting all anchor links on a page allows scraping tools to recursively crawl a site:
// Get all links on page
const links = document.querySelectorAll(‘a‘);
// Extract hrefs
const hrefs = Array.from(links).map(a => a.href);
// Recursively visit each link
hrefs.forEach(url => visitPage(url));Testing and Automation
For QA engineers automating user flows, accessing href values facilitates simulated clicks:
// Get login link
const loginLink = document.querySelector(‘a[href*="login"]‘);
// Simulate click
loginLink.click(); These are just a few examples of how getting elements by attributes aids test and production automation.
Key Methods for Getting Elements by Attribute
Now that we‘ve seen some practical use cases, let‘s explore the JavaScript techniques for getting elements by their href or other attributes.
1. querySelector() and querySelectorAll()
The querySelector method allows CSS selector queries similar to jQuery:
const link = document.querySelector(‘a[href="https://example.com"]‘); This returns the first matching with that exact href value.
For getting all matching elements, there is querySelectorAll():
const links = document.querySelectorAll(‘a[href*="subdomain"]‘); This returns a NodeList of all links containing "subdomain".
2. getAttribute() on Individual Elements
If you already have a reference to the element, you can directly access the href using getAttribute():
// Get first <a>
const link = document.querySelector(‘a‘);
if (link.getAttribute(‘href‘) === ‘#home‘) {
// Homepage link
}3. Comparing Techniques: Pros vs Cons
| Method | Pros | Cons |
|---|---|---|
| querySelector | Simple syntax, similar to jQuery Fast lookup of single match |
Limited older browser support |
| getAttribute | Simple, avoids DOM crawling if already have reference Get other attributes besides href |
Requires existing reference to element |
| getElementsByTagName | No browser compatibility issues Access all elements by tag name |
Requires iteration code No attribute filtering |
So in summary, querySelector() provides the most flexible standalone lookup based on complex selectors. But getAttribute() can be useful for getting hrefs in code that already accesses element(s).
Additional Examples and Techniques
Here are some more examples demonstrating practical applications of getting anchors by hrefs.
Finding Broken Links by Status Code
This snippet detects broken links by attempting HEAD requests and checking status codes:
// Get all links
const links = document.querySelectorAll(‘a‘);
// Check each href
const brokenLinks = [];
links.forEach(link => {
const href = link.getAttribute(‘href‘);
fetch(href, { method: ‘HEAD‘ })
.then(res => {
if (res.status >= 400) {
brokenLinks.push(href);
}
});
});Tracking Outbound Links and Downloads
This pattern allows tracking clicks on outbound links and file downloads:
document.addEventListener(‘click‘, e => {
const el = e.target;
if (el.tagName === ‘A‘) {
const href = el.getAttribute(‘href‘);
// Track outbound links
if (href.startsWith(‘http‘)) {
trackOutboundLink(href);
}
// Track downloads
else if (href.endsWith(‘.zip‘)) {
trackDownload(el.innerText);
}
}
});This technique could be extended for analytics purposes on anchor tags.
Utility Function for Robust Attribute Selecting
Here is a reusable utility that handles common edge cases:
// @param {string} attr Attribute name
// @param {string} value Value to match
// @param {Element} context DOM subtree
function getElementsByAttribute(attr, value, context = document) {
const iterable = context.querySelectorAll(`[${attr}="${value}"]`);
const elements = [];
let el;
for (el of iterable) {
elements.push(el);
}
if (elements.length < 1) {
return null;
}
return elements;
}
// Usage:
const links = getElementsByAttribute(‘href‘, pageUrl); This encapsulates querying, handling no matches, iteration, and return value as reusable logic.
Conclusion
Finding HTML elements based on attribute values like hrefs is a common task. As seen, the querySelector method provides a simple yet flexible approach similar to jQuery selectors. Meanwhile, directly reading the href attribute offers value when individual elements already in hand.
Taking advantage of these patterns allows robust selection logic to support use cases like automation, event handling, scraping, and more. With the techniques covered, you should have no problem getting elements by associated href attribute values.
