PerformanceResourceTiming: contentType property

A string indicating the MIME type "essence" of the content. This may be one of the following values:

text/javascript

JavaScript content.

application/json

JSON content.

image/svg+xml

SVG content.

application/xml

XML content (other than SVG).

MIME type/subtype

Any other MIME type/subtype supported by the user agent.

"" (empty string)

Returned for MIME types that are not supported by the browser, or if the resource fetch failed due to CORS checks.

The contentType property can be used to get specific resource timing entries only; for example, only those related to scripts.

The following example uses a PerformanceObserver to notify of new resource performance entries as they are recorded in the browser's performance timeline. The buffered option is used for accessing entries from before the observer creation.

const observer = new PerformanceObserver((list) => {
  const javascriptResources = list.getEntries().filter((entry) => {
    return entry.contentType === "text/javascript";
  });
  console.log(javascriptResources);
});

observer.observe({ type: "resource", buffered: true });

The following example uses Performance.getEntriesByType(), which only shows resource performance entries present in the browser's performance timeline at the time you call the method.

const scripts = performance.getEntriesByType("resource").filter((entry) => {
  return entry.contentType === "text/javascript";
});
console.log(scripts);