Implementing caching in an API function Last updated: 07. Apr 2025

This function implements caching for an API endpoint by checking the 'If-Modified-Since' header and returning a 304 status if the content has not been modified.

Implementation steps:

Server-Side (API): setHeader "Last-Modified" and check If-Modified-Since
Client-Side: Make sure caching is enabled (if so, nothing needs to be changed)
Testing: Make sure you haven't disabled caching in the developer toolbar

1. Server-Side: setHeader "Last-Modified" and check If-Modified-Since

// Format the site's last modified date
let formattedSiteModifiedDate = docly.format(request.sitemodified, "R");
docly.setHeader("Last-Modified", formattedSiteModifiedDate);

// Retrieve the 'If-Modified-Since' header from the request
let ifModifiedSinceHeader = docly.getHeader("If-Modified-Since");
if (ifModifiedSinceHeader) {
    // Convert the 'If-Modified-Since' header to a Date object
    let ifModifiedSinceDate = new Date(ifModifiedSinceHeader);

    // Calculate the difference between the 'If-Modified-Since' date and the site's last modified date
    let dateDifference = docly.dateDiff(ifModifiedSinceDate, request.sitemodified);
    
    // If the difference in seconds is less than 1, set the result code to 304 (Not Modified)
    if (dateDifference.TotalSeconds < 1) {
        let formattedSiteModifiedDate = docly.format(request.sitemodified, "R");
        docly.setHeader("Last-Modified", formattedSiteModifiedDate);
        return docly.setResultCode(304);
    }
}

// Return an embedded file?
// docly.downloadEmbeded(file, embeddedId, "filename.pdf");

// Return what ever object you want here (not cached)
return {
    "ifModified": ifModifiedSinceHeader,
    "siteModified": formattedSiteModifiedDate,
    "diff": dateDifference.TotalSeconds
};

2. Client-Side: Make sure caching is enabled (if so, nothing needs to be changed)

Modern browsers generally cache responses based on HTTP headers (like `Last-Modified` or `ETag`). While the standard `fetch` API respects these headers, jQuery's AJAX functions (like `$.get` or `$.ajax`) might append a cache-busting parameter (`_={timestamp}`) by default for certain data types.

To ensure caching is allowed for a `$.get` request, explicitly set the `cache` option to `true`:

// Example: Using $.get with caching explicitly enabled
$.get("API/test", {
  cache: true // Set cache to true to allow browser caching
}).then(function(data) {
   // Handle the response data here
   console.log("Data received:", data);
}).fail(function(jqXHR, textStatus, errorThrown) {
   // Handle errors
   console.error("Request Failed:", textStatus, errorThrown);
});

3. Testing: Make sure you haven't disabled caching in the developer toolbar

When testing API caching, ensure that the "Disable cache" option is **not** checked in your browser's developer toolbar. This setting is typically found under the "Network" tab.