Use XHR/fetch Breakpoints!
Web debugging tools are so incredibly excellent these days. I remember the days where they didn't exist and debugging was a total nightmare, even for the simplest of problems. A while back I introduced many of you to Logpoints, a way to output console.log messages without needing to change the source files. Another great breakpoint type is XHR/fetch breakpoints, allowing you to pause execution when an AJAX call is made. Let's look at XHR/fetch breakpoints!
To set an XHR/fetch breakpoint, open your browser's Developer Tools and click the Sources tab -- the same tab you open for other breakpoints. Under the XHR/fetch accordion item, click the big "+" button. You'll see an empty text input:
Within that text input, type a string that you'd like to break all XHR/fetch calls on. For example, if I wanted to break any time a fetch request was made, I would input davidwalsh.name:
In the case above, a XHR/fetch request breakpoint halts execution because a request is made to https://davidwalsh.name/url-canparse. You'll be able to step through and step into like you can with regular breakpoints, and you'll get a full Call Stack pane to see how execution got to a given point.
XHR/fetch breakpoints are another great way to debug your web app. The more reliant we are on dynamic websites with frequently changing content, debugging fetch calls is a must. Happy debugging!
// Function to make an XHR request to a fake API function makeXHRRequest() { const xhr = new XMLHttpRequest(); xhr.open('GET', 'https://jsonplaceholder.typicode.com/posts/1', true); // Set a breakpoint here to inspect xhr object // debugger; xhr.onload = function () { if (xhr.status === 200) { const response = JSON.parse(xhr.responseText); console.log('XHR Response:', response); // Set a breakpoint here to inspect the response // debugger; } else { console.error('XHR Request failed with status:', xhr.status); } }; xhr.send(); } // Function to make a fetch request to a fake API async function makeFetchRequest() { // Set a breakpoint here to inspect fetch options // debugger; try { const response = await fetch('https://jsonplaceholder.typicode.com/posts/2'); if (!response.ok) { throw new Error(Fetch Request failed with status: ${response.status}); } const data = await response.json(); console.log('Fetch Response:', data); // Set a breakpoint here to inspect the data // debugger; } catch (error) { console.error('Fetch Request Error:', error); } } // Call the XHR and Fetch functions makeXHRRequest(); makeFetchRequest();