Feature-detect availability of viewTypes property in browser.menus API

detect-menus-viewTypes.js

// Example: How to feature-detect a new property (viewTypes) in the menus API
// Feature introduced in Firefox 64.
// See https://bugzilla.mozilla.org/show_bug.cgi?id=1416839

// // Minimal usage example:
// let menuCreateParams = {
//   title: "some menu item meant for the sidebar",
//   viewTypes: ["sidebar"],
// };
// if (!supportsMenuViewTypes()) {
//   // Not supported, fall back to showing the menu everywhere?
//   delete menuCreateParams.viewTypes;
// }
// browser.menus.create(menuCreateParams);

// Note: If used more than once, cache the result by storing it in a variable.
function supportsMenuViewTypes() {
  try {
    // The validation of API parameters in the WebExtensions API is often done
    // synchronously (optionally followed by extra asynchronous validation).
    // When an unsupported property is passed, an error is thrown.

    // This characteristic can be used to perform feature detection rather
    // easily: Call the method with a parameter and check if the call throws.

    // In the example below, we use browser.menus.update with a non-existing
    // menu ID, because such calls with non-existing menu IDs are silently
    // ignored, so this feature detection method has no side effects.

    browser.menus.update("unique ID that is not used for a real menu", {
      // Just checking whether the property is supported.
      // Optionally, you can also add an explicit value such as ["sidebar"]
      // to see if that specific value is supported.
      viewTypes: [],
    });
    return true;
  } catch (e) {
    return false;
  }
}