Add Get The First Item For Every Top-Level Key as a jq TIL

README.md

@@ -10,7 +10,7 @@ pairing with smart people at Hashrocket.
 
 For a steady stream of TILs, [sign up for my newsletter](https://crafty-builder-6996.ck.page/e169c61186).
 
-_1298 TILs and counting..._
+_1299 TILs and counting..._
 
 ---
 
@@ -490,6 +490,7 @@ _1298 TILs and counting..._
 - [Extract A List Of Values](jq/extract-a-list-of-values.md)
 - [Find All Objects In An Array Where Key Is Set](jq/find-all-objects-in-an-array-where-key-is-set.md)
 - [Find All Objects With A Matching Key Value Pair](jq/find-all-objects-with-a-matching-key-value-pair.md)
+- [Get The First Item For Every Top-Level Key](jq/get-the-first-item-for-every-top-level-key.md)
 - [Reduce Object To Just Entries Of A Specific Type](jq/reduce-object-to-just-entries-of-a-specific-type.md)
 
 ### Kitty

jq/get-the-first-item-for-every-top-level-key.md

@@ -0,0 +1,37 @@
+# Get The First Item For Every Top-Level Key
+
+Let's say we have a JSON object where each key in that object is tied to a
+large array of values. To get a better idea of what the data looks like, we
+want to trim down the JSON a bit. Essentially, we want to tie each key to the
+first value in each of their respective arrays.
+
+We can do this by reducing the object into a new object where each top-level
+key is tied to the first item in its array.
+
+```bash
+$ jq '. as $object | reduce keys[] as $k ({}; .[$k] = $object[$k][0])' data.json
+```
+
+This uses variables (`$object` and `$k`) and the [`reduce`
+function](https://stedolan.github.io/jq/manual/#Reduce) to iterate over the
+incoming JSON object and produce a new object with the trimmed down data.
+
+JSON like this:
+
+```json
+{
+  "key1": ["a", "b", "c"],
+  "key2": [1, 2, 3],
+  "key3": ["x", "y", "z"]
+}
+```
+
+will be turned into this:
+
+```json
+{
+  "key1": "a",
+  "key2": 1,
+  "key3": "x"
+}
+```