Add Include Type Of Operation In Webhook Response as a GROQ til

README.md

@@ -10,7 +10,7 @@ pairing with smart people at Hashrocket.
 
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-_1195 TILs and counting..._
+_1196 TILs and counting..._
 
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@@ -340,6 +340,7 @@ _1195 TILs and counting..._
 ### GROQ
 
 - [Grab Values From An Array Of References](groq/grab-values-from-an-array-of-references.md)
+- [Include Type Of Operation In Webhook Response](groq/include-type-of-operation-in-webhook-response.md)
 
 ### Heroku
 

groq/include-type-of-operation-in-webhook-response.md

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+# Include Type Of Operation In Webhook Response
+
+When setting up a webhook in Sanity Studio, you can specify what types of
+operations you want to trigger the webhook: `create`, `update`, and `delete`.
+
+If you include all three for a webhook, then you'll probably want to know in
+your webhook handler which type of operation you're receiving.
+
+Webhooks are run in _Delta Mode_ which means that a collection of GROQ
+functions are available in the _filter_ and _projection_ blocks. These
+functions include
+[`delta::operation`](https://www.sanity.io/docs/groq-functions#a64594a50318).
+
+Here is what a projection using `delta::operation` might look like:
+
+```groq
+{
+  _id,
+  firstName,
+  lastName,
+  email,
+  'operation': delta::operation()
+}
+```
+
+This function can resolve to either `create`, `update`, or `delete`.