xhr.onreadystatechange = function()
{
if ( xhr.readyState == 4 )
{
if (xhr.status == 200)
{
// Process returned data (eg: Parse XML).
// Check status of result depending on custom/ad-hoc error detection.
// -- most commonly a 0 for fail, or 1 for pass
// Deal with/report error, or take some other action based upon returned data.
}
}
}
The above approach works, but as your application grows and your need to provide useful error reporting (and error avoidance!) increases, the good ol’ boolean-style error checking will quickly become unwieldy. I can see it now…
- Developer 1:
What does an error code of 7 mean again?
- Developer 2:
Ummm, Hang on, I’m sure we wrote that down somewhere…
Fear not, there’s a much smarter alternative, one which you rely upon every time you load up your browser—HTTP Status Codes (check out Mark Pilgrim’s humourous abridged list if the thought of reading yet another RFC sends you into an glazed-eyed stupor).
Taking the previous example, I’ve added a switch
block for some of the status codes that will be most useful in handling the response to your JavaScript HTTP request:
xhr.onreadystatechange = function()
{
if ( xhr.readyState == 4 )
{
switch ( xhr.status )
{
case 200: // OK!
/*
* If the request was to create a new resource
* (such as post an item to the database)
* You could instead return a status code of '201 Created'
*/
break;
case 304: // Not Modified
/*
* This would be used when your Ajax widget is
* checking for updated content,
* such as the Twitter interface.
*/
break;
case 400: // Bad Request
/*
* A bit like a safety net for requests by your JS interface
* that aren't supported on the server.
* "Your browser made a request that the server cannot understand"
*/
break;
case 409: // Conflict
/*
* Perhaps your JavaScript request attempted to
* update a Database record
* but failed due to a conflict
* (eg: a field that must be unique)
*/
break;
case 503: // Service Unavailable
/*
* A resource that this request relies upon
* is currently unavailable
* (eg: a file is locked by another process)
*/
break;
}
}
}
So the next time you’re about to stick <status>1</status>
or similar into an XML response, take a deeper look into HTTP Status Codes. It might be the first step towards getting some REST, which is most certainly a Good Thing™.
Frequently Asked Questions (FAQs) about AJAX Errors
What is a 400 Bad Request Error in AJAX?
A 400 Bad Request Error in AJAX is a client-side error that occurs when the server is unable to understand the request due to invalid syntax. This error can be triggered by various reasons such as incorrect data format sent in a request, size of the request is too large, or issues with the server itself. It’s important to debug the error to identify the root cause and apply the appropriate solution.
How can I debug a 400 Bad Request Error in AJAX?
Debugging a 400 Bad Request Error in AJAX involves several steps. First, check the syntax of your AJAX request. Ensure that the URL, headers, and data are correctly formatted. Use browser developer tools to inspect the network request and response. If the error persists, check the server-side code for any issues.
How can I fix a 400 Bad Request Error in AJAX?
Fixing a 400 Bad Request Error in AJAX depends on the cause of the error. If the error is due to incorrect data format, ensure that the data is correctly formatted as JSON or XML. If the request size is too large, consider reducing the size of the request. If the error is due to server-side issues, check the server logs for any errors and fix them accordingly.
Why am I getting a 400 Bad Request Error in jQuery AJAX POST?
A 400 Bad Request Error in jQuery AJAX POST can occur due to several reasons. The most common reason is incorrect data format. Ensure that the data is correctly formatted as JSON or XML. Other reasons can include issues with the server or the size of the request being too large.
How can I prevent a 400 Bad Request Error in AJAX?
Preventing a 400 Bad Request Error in AJAX involves ensuring that the AJAX request is correctly formatted. This includes the URL, headers, and data. Also, ensure that the size of the request is not too large. Regularly check the server logs for any errors and fix them promptly.
What is the impact of a 400 Bad Request Error in AJAX on my website?
A 400 Bad Request Error in AJAX can negatively impact your website by causing functionality issues. This can lead to a poor user experience and potentially loss of users or customers. Therefore, it’s important to promptly identify and fix any 400 Bad Request Errors.
How can I handle a 400 Bad Request Error in AJAX in WordPress?
Handling a 400 Bad Request Error in AJAX in WordPress involves checking the AJAX request and the server-side code. Ensure that the AJAX request is correctly formatted and the server-side code is error-free. Use the WordPress debugging tools to help identify and fix any issues.
Why am I getting a 400 Bad Request Error on AJAX call in WordPress?
A 400 Bad Request Error on AJAX call in WordPress can occur due to several reasons. The most common reason is incorrect data format. Ensure that the data is correctly formatted as JSON or XML. Other reasons can include issues with the server or the size of the request being too large.
How can I debug a 400 Bad Request Error on AJAX call in WordPress?
Debugging a 400 Bad Request Error on AJAX call in WordPress involves checking the AJAX request and the server-side code. Use the WordPress debugging tools to help identify and fix any issues. Also, check the server logs for any errors.
How can I fix a 400 Bad Request Error on AJAX call in WordPress?
Fixing a 400 Bad Request Error on AJAX call in WordPress involves identifying the cause of the error and applying the appropriate solution. This can include correcting the data format, reducing the size of the request, or fixing any server-side issues. Use the WordPress debugging tools to help identify and fix any issues.
Andrew is a UI developer at 99designs.