Add Check If An Object Is Empty With Zod as a JavaScript 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).
 
-_1238 TILs and counting..._
+_1241 TILs and counting..._
 
 ---
 
@@ -344,6 +344,7 @@ _1238 TILs and counting..._
 
 - [Grab Multiple Values From A Reference](groq/grab-multiple-values-from-a-reference.md)
 - [Grab Values From An Array Of References](groq/grab-values-from-an-array-of-references.md)
+- [Include Attributes When Conditional Check Passes](groq/include-attributes-when-conditional-check-passes.md)
 - [Include Type Of Operation In Webhook Response](groq/include-type-of-operation-in-webhook-response.md)
 
 ### Heroku
@@ -384,6 +385,7 @@ _1238 TILs and counting..._
 - [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)
 - [Check If A Number Is Positive Or Negative](javascript/check-if-a-number-is-positive-or-negative.md)
+- [Check If An Object Is Empty With Zod](javascript/check-if-an-object-is-empty-with-zod.md)
 - [Check If Something Is An Array](javascript/check-if-something-is-an-array.md)
 - [Check The Password Confirmation With Yup](javascript/check-the-password-confirmation-with-yup.md)
 - [Compare The Equality Of Two Date Objects](javascript/compare-the-equality-of-two-date-objects.md)
@@ -1141,6 +1143,7 @@ _1238 TILs and counting..._
 - [Extract Object Type Values Into A Union Type](typescript/extract-object-type-values-into-a-union-type.md)
 - [Generate Inferred Type From Zod Schema](typescript/generate-inferred-type-from-zod-schema.md)
 - [Interfaces With The Same Name Are Merged](typescript/interfaces-with-the-same-name-are-merged.md)
+- [Narrow The Type Of An Array To Its Values](typescript/narrow-the-type-of-an-array-to-its-values.md)
 - [Re-Export An Imported Type](typescript/re-export-an-imported-type.md)
 - [Type Narrowing With Const VS Let Strings](typescript/type-narrowing-with-const-vs-let-strings.md)
 - [Type Narrowing With Similarly Shaped Objects](typescript/type-narrowing-with-similarly-shaped-objects.md)

groq/include-attributes-when-conditional-check-passes.md

@@ -0,0 +1,40 @@
+# Include Attributes When Conditional Check Passes
+
+The graph-like nature of Sanity means that you'll often be querying for data
+that spans a variety of document types. For instance, your front-end could be
+requesting content in the shape of a blog post, video, and podcast. Though
+there are some similarities, each of these document types will have some unique
+attributes.
+
+When using GROQ to query for data that spans different types of documents, you
+can use [a conditional query
+syntax](https://www.sanity.io/docs/query-cheat-sheet#64a36d80be73) to include
+type-specific attributes.
+
+```groq
+*[_type == 'blog' || _type == 'video' || _type == 'podcast'][]{
+  title,
+  'slug': slug.current,
+  _type == 'blog' => {
+    body,
+    read_time
+  },
+  _type == 'video' => {
+    description,
+    mp4_url
+  },
+  _type == 'podcast' => {
+    description,
+    mp3_url
+  }
+}
+```
+
+Notice that there are some attributes that are common across each type (i.e.
+`title` and `slug`). Each type then has attributes unique to its document type
+(i.e. `blog` has `body` and `read_time`).
+
+This conditional query syntax allows us to both define flexible schemas in
+Sanity and then query against that flexible schema.
+
+[source](https://www.youtube.com/watch?v=dCGPNkcTseQ)

javascript/check-if-an-object-is-empty-with-zod.md

@@ -0,0 +1,29 @@
+# Check If An Object Is Empty With Zod
+
+Zod is a schema validation library. It can be used to check all sorts of
+properties about the data moving through our system.
+
+Let's look at how to implement a common type of check -- is this object empty?
+
+```javascript
+import {z} from 'zod';
+
+const emptyObjectSchema = z.object({}).strict();
+const isEmpty = (obj: object): boolean => {
+  const result = emptyObjectSchema.safeParse(obj);
+  return result.success;
+}
+
+isEmpty({});
+//=> true
+
+isEmpty({ hello: 'world' });
+//=> false
+```
+
+This `emptyObjectSchema` _strictly_ defines the schema as an empty object
+(`{}`). Without the [`strict()`](https://github.com/colinhacks/zod#strict)
+part, we'd be allowing an object with key-value pairs to quietly pass the
+validation.
+
+[source](https://twitter.com/jbrancha/status/1565728882082385920)

typescript/narrow-the-type-of-an-array-to-its-values.md

@@ -0,0 +1,39 @@
+# Narrow The Type Of An Array To Its Values
+
+When an array of string values is defined in a TypeScript context, the inferred
+type will be `string[]`. That's because the values of an array can be
+reassigned. The most precise TypeScript can be is to say that it is an array of
+string.
+
+```typescript
+const actions = ['increase', 'decrease'];
+// typeof actions => string[]
+```
+
+We can freeze the array with its values using `as const`, the [const
+assertion](https://www.typescriptlang.org/docs/handbook/release-notes/typescript-3-4.html#const-assertions).
+This doesn't actually _freeze_ the array, but it does mark it as `readonly` for
+the TypeScript compiler.
+
+That means we can lean on the compiler for a lot more specific feedback.
+Consider for instance this `reducer` function.
+
+```typescript
+const actions = ['increase', 'decrease'] as const
+
+const reducer = (action: typeof actions[number]) => {
+  switch (action) {
+    case 'increase':
+      // do an increase
+    case 'decrease':
+      // do a decrease
+    case 'submit': // TYPE ERROR, "submit" is not comparable to type 'increase' | 'decrease'
+      // do a submit
+    default:
+      throw Error('Unrecognized action!')
+  }
+}
+
+// TYPE ERROR, "submit" is not comparable to type 'increase' | 'decrease'
+reducer('submit')
+```