The problem of XMLHttpRequest validity in AJAX development

Ajax|request|xml|xmlhttprequest| problem

One of the biggest problems that Ajax developers face is how to react when XMLHttpRequest is unavailable.

Although most modern browsers support XMLHttpRequest, there are a small number of users whose browsers do not support it, or prevent the use of XMLHttpRequest because of browser security settings. Therefore, you should try to ensure that the application system "normal demotion" use, in the system to retain the browser does not support XMLHttpRequest features.

In the shopping cart example, the best way to do this is to have an add to cart button that allows for regular submission and refreshes the page to reflect changes in the status of the cart. Ajax XMLHttpRequest can be added to the page by JavaScript when the page is loaded, with the JavaScript handler function for each add to cart button only if it is available.

Another approach is to detect xmlhttprequest when a user logs on, and then decide whether to provide an AJAX version or a regular form-submitted version.