How Can I Tell if My AJAX Response is JSON Data or an Error?

How to Determine if a Received AJAX Response is JSON or an Error Message?

AJAX calls may return either a JSON string containing data or an error message generated by a server-side function (e.g., PHP's mysql_error()). Distinguishing between these responses is crucial for proper data handling.

Using JSON.parse to Test for JSON Responses

To determine if a response string represents JSON, we can leverage the JSON.parse() method. This method attempts to parse the string as a JSON object. If successful, it returns an object; otherwise, it throws an exception.

function isJson(str) {
    try {
        JSON.parse(str);
    } catch (e) {
        return false;
    }
    return true;
}

With this function, you can test the response string using the following code:

if (isJSON(data)){
    // Parse the data as JSON and proceed with data operations
}else{
    // Display the error message in an alert
    alert(data);
}

This approach allows for cleaner and more robust code by separating the handling of JSON data and error messages.

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