Chapter 18. Diagnosis

IF THERE'S ONE CERTAINTY IN THE LIFE OF A DEVELOPER, IT'S BUGS. AJAX PROGRAMMING ISN'T ROCKET science, but you can still expect the odd moment of pain during development and maybe even in production. Fortunately, there are plenty of techniques, tools, and libraries available to help you isolate problems as they arise. This chapter breaks them into four categories.

Logging is just good old logging applied to the browser, where log messages can be shown in a popup, uploaded to the server, or shown in some browser-specific way. Likewise, Debugging is general-purpose debugging applied to JavaScript that is running within the browser.

The next two patterns are more Ajax-specific. DOM Inspection is about analyzing the dynamic state of the DOM. Traffic Sniffing is about watching traffic between browser and server.