How can I Detect and Handle Navigation Changes in a Webpage Using JavaScript?

Handling Navigation Changes with Event Listeners

When the user navigates to a new URL within a webpage, it can be challenging to capture the event and access the DOM of the newly loaded page. To address this, we will explore a solution using JavaScript's powerful observer API.

Observing DOM Mutations
Instead of relying on timeouts or polling, we can utilize a MutationObserver to monitor changes to the DOM tree. By observing the element, we can detect when the page content has been modified due to an altered location.href.

Example Implementation
Here's a code snippet that demonstrates the use of MutationObserver to monitor window.location.href changes:

<code class="javascript">var oldHref = document.location.href;

window.onload = function() {
    var bodyList = document.querySelector('body');

    var observer = new MutationObserver(function(mutations) {
        if (oldHref != document.location.href) {
            oldHref = document.location.href;
            /* Changed ! your code here */
        }
    });
    
    var config = {
        childList: true,
        subtree: true
    };
    
    observer.observe(bodyList, config);
};</code>

Latest JavaScript Specification
In modern JavaScript, you can use arrow functions and a slightly simplified syntax to achieve the same functionality:

<code class="javascript">const observeUrlChange = () => {
  let oldHref = document.location.href;
  const body = document.querySelector('body');
  const observer = new MutationObserver(mutations => {
    if (oldHref !== document.location.href) {
      oldHref = document.location.href;
      /* Changed ! your code here */
    }
  });
  observer.observe(body, { childList: true, subtree: true });
};

window.onload = observeUrlChange;</code>

By using this event-driven approach, you can avoid polling or timeouts and capture URL changes in a performant and reliable manner. This enables you to access the DOM of the newly loaded page and execute your desired actions whenever the user navigates within the same webpage.

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