Add Add Item To An Array Of References In Sanity as a JavaScript TIL

README.md

@@ -10,7 +10,7 @@ pairing with smart people at Hashrocket.
 
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-_1346 TILs and counting..._
+_1347 TILs and counting..._
 
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@@ -402,6 +402,7 @@ _1346 TILs and counting..._
 ### JavaScript
 
 - [Accessing Arguments To A Function](javascript/accessing-arguments-to-a-function.md)
+- [Add Item To An Array Of References In Sanity](javascript/add-item-to-an-array-of-references-in-sanity.md)
 - [Basic Date Formatting Without A Library](javascript/basic-date-formatting-without-a-library.md)
 - [Character Codes from Keyboard Listeners](javascript/character-codes-from-keyboard-listeners.md)
 - [Check Classes On A DOM Element](javascript/check-classes-on-a-dom-element.md)

javascript/add-item-to-an-array-of-references-in-sanity.md

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+# Add Item To An Array Of References In Sanity
+
+Let's say we have an existing record in our Sanity dataset. The schema for that
+record allows for an array of references to another type of record. As part of
+programmatically importing some data, we need to tie some records together by
+adding to that array of references.
+
+We've already set up our [Sanity client](https://www.sanity.io/docs/js-client)
+(via the JavaScript SDK). We have an `_id` for the record we want to patch. We
+have a `resourceId` for the resource that we want to _reference_ in the array.
+
+Here is how we perform that `patch`:
+
+```javascript
+await sanityClient
+  .patch(_id)
+  .setIfMissing({resources: []})
+  .append('resources', [{_type: 'reference', _ref: resourceId}])
+  .commit({autoGenerateArrayKeys: true})
+```
+
+1. We give it the `_id` of the record we want to `patch`.
+2. We set our array of `resources` to an empty array (`[]`) if it hasn't
+   already been set.
+3. We `append` to the `resources` array with an array containing a single item,
+   a reference to our resource.
+4. We `commit` the changes with the directive that Sanity should auto-generate
+   the `_key` value for any new array items.