guide: add String example usage to supported types

examples/guide-supported-types-examples/src/lib.rs

@@ -6,3 +6,4 @@ extern crate wasm_bindgen;
 pub mod imported_types;
 pub mod exported_types;
 pub mod str;
+pub mod string;

examples/guide-supported-types-examples/src/string.rs

@@ -0,0 +1,17 @@
+use wasm_bindgen::prelude::*;
+
+#[wasm_bindgen]
+pub fn take_string_by_value(x: String) {}
+
+#[wasm_bindgen]
+pub fn return_string() -> String {
+    "hello".into()
+}
+
+#[wasm_bindgen]
+pub fn take_option_string(x: Option<String>) {}
+
+#[wasm_bindgen]
+pub fn return_option_string() -> Option<String> {
+    None
+}

examples/guide-supported-types-examples/string.js

@@ -0,0 +1,22 @@
+import {
+  take_string_by_value,
+  return_string,
+  take_option_string,
+  return_option_string,
+} from './guide_supported_types_examples';
+
+take_string_by_value('hello');
+
+let s = return_string();
+console.log(typeof s); // "string"
+
+take_option_string(null);
+take_option_string(undefined);
+take_option_string('hello');
+
+let t = return_option_string();
+if (t == null) {
+  // ...
+} else {
+  console.log(typeof s); // "string"
+}

guide/src/reference/types.md

@@ -73,6 +73,18 @@ Copies the string's contents back and forth between the JavaScript
 garbage-collected heap and the Wasm linear memory with `TextDecoder` and
 `TextEncoder`
 
+### Example Rust Usage
+
+```rust
+{{#include ../../../examples/guide-supported-types-examples/src/string.rs}}
+```
+
+### Example JavaScript Usage
+
+```js
+{{#include ../../../examples/guide-supported-types-examples/string.js}}
+```
+
 ## `char`
 
 | `T` parameter | `&T` parameter | `&mut T` parameter | `T` return value | `Option<T>` parameter | `Option<T>` return value | JavaScript representation |