Add Find All Objects In An Array Where Key Is Set as a jq TIL

jq/find-all-objects-in-an-array-where-key-is-set.md

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+# Find All Objects In An Array Where Key Is Set
+
+Let's say we have a large array of objects. And the data in those objects,
+while generally having the same shape, does not always have certain values set.
+
+For instance, here is some data where the `token` is sometimes set, sometimes
+`null`, and sometimes missing altogether.
+
+```json
+[
+  {
+    "id": 1,
+    "token": "abc"
+  },
+  {
+    "id": 3,
+    "token": null
+  },
+  {
+    "id": 5
+  },
+  ...
+]
+```
+
+We can find out how many objects in this collection have the `token` key set to
+an actual value with [a `jq` query](https://stedolan.github.io/jq/manual) like
+the following.
+
+```bash
+jq '. | map(select(has("token") and .token != null)) | length' data.json
+```
+
+This maps over each object selecting those where it has `token` and `token` is
+not `null`.
+
+We can instead produce the inverse count—those objects where `token` is not set
+to a value—with the `not` operator.
+
+```bash
+jq '. | map(select(has("token") and .token != null | not)) | length' data.json
+```
+
+If you want to inspect the array of objects that either of these queries filters down to, you can drop the `| length` part.
+
+```bash
+jq '. | map(select(has("token") and .token != null))' data.json
+```
+
+Here is [a live example](https://jqterm.com/?query=.%20%7C%20map%28select%28has%28%22token%22%29%20and%20.token%20!%3D%20null%20%7C%20not%29%29).