Merge pull request #319 from kevanstannard/syntax-lookup-switch

Syntax lookup: Switch

Author: ryyppy

misc_docs/syntax/language_switch.mdx

@@ -0,0 +1,45 @@
+---
+id: "switch"
+keywords: ["switch", "pattern", "match"]
+name: "switch"
+summary: "This is the `switch` expression keyword."
+category: "languageconstructs"
+---
+
+A `switch` expression allows you to match / destructure almost any kind of value (array, list, records, strings, numbers, variants, etc). Each branch (pattern) of a `switch` expression must return a value of the same type.
+
+### Example
+
+<CodeTab labels={["ReScript", "JS Output"]}>
+
+```res
+type shape = Circle(float) | Square(float)
+
+let shape = Square(3.0)
+
+let message = switch shape {
+| Circle(radius) => "Circle with radius " ++ Js.Float.toString(radius)
+| Square(length) => "Square with sides of length " ++ Js.Float.toString(length)
+}
+```
+
+```js
+var shape = {
+  TAG: /* Square */ 1,
+  _0: 3.0,
+};
+
+var message;
+
+message =
+  shape.TAG === /* Circle */ 0
+    ? "Circle with radius " + (3.0).toString()
+    : "Square with sides of length " + (3.0).toString();
+```
+
+</CodeTab>
+
+
+### References
+
+* [Switch Based on Shape of Data](/docs/manual/latest/pattern-matching-destructuring#switch-based-on-shape-of-data)