From ef5a27f5a1bf416546240e92664cb5e3ea752f82 Mon Sep 17 00:00:00 2001
From: jaywcjlove <398188662@qq.com>
Date: Sat, 12 Nov 2022 14:25:47 +0800
Subject: [PATCH] doc: update `typescript.md`.

---
 docs/typescript.md | 43 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 43 insertions(+)

diff --git a/docs/typescript.md b/docs/typescript.md
index e209e6b..887ce25 100644
--- a/docs/typescript.md
+++ b/docs/typescript.md
@@ -1264,3 +1264,46 @@ class Select<T> extends React.Component<SelectProps<T>, any> {}
 // 使用
 const Form = () => <Select<string> items={['a', 'b']} />;
 ```
+
+各种各样的技巧
+---
+
+### keyof 取 interface 的键
+<!--rehype:wrap-class=row-span-2-->
+
+```ts
+interface Point {
+    x: number;
+    y: number;
+}
+ 
+// type keys = "x" | "y"
+type keys = keyof Point;
+```
+
+### 索引签名
+
+```ts
+interface NumberOrString {
+  [index: string]: string | number;
+  length: number;
+  name: string;
+}
+```
+
+### 从数组中提取类型
+
+```ts
+type Point = { x: number; y: number; }
+type Data = Point[];
+// Data 是个数组，提取里面的元素类型
+type PointDetail = Data[number];
+// type PointDetail = { x: number; y: number; }
+```
+
+### 只读元组类型
+
+```ts
+const point = [3, 4] as const
+// type 'readonly [3, 4]'
+```