From d7857da2628c67792cadcc97dd5e6239e65ca9ec Mon Sep 17 00:00:00 2001
From: Tomohide Takao <amakunai.dorayaki@gmail.com>
Date: Wed, 11 Jul 2018 07:20:52 +0900
Subject: [PATCH] binding for Array.prototype.map()

---
 src/js.rs                     | 10 ++++++++++
 tests/all/js_globals/Array.rs | 34 ++++++++++++++++++++++++++++++++++
 2 files changed, 44 insertions(+)

diff --git a/src/js.rs b/src/js.rs
index 08143ad93..24789b66b 100644
--- a/src/js.rs
+++ b/src/js.rs
@@ -216,6 +216,16 @@ extern "C" {
     #[wasm_bindgen(method, getter, structural)]
     pub fn length(this: &Array) -> u32;
 
+    /// map calls a provided callback function once for each element in an array, 
+    /// in order, and constructs a new array from the results. callback is invoked 
+    /// only for indexes of the array which have assigned values, including undefined. 
+    /// It is not called for missing elements of the array (that is, indexes that have 
+    /// never been set, which have been deleted or which have never been assigned a value).
+    /// 
+    /// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/map
+    #[wasm_bindgen(method)]
+    pub fn map(this: &Array, predicate: &mut FnMut(JsValue, u32, Array) -> JsValue) -> Array;
+
     /// The pop() method removes the last element from an array and returns that
     /// element. This method changes the length of the array.
     ///
diff --git a/tests/all/js_globals/Array.rs b/tests/all/js_globals/Array.rs
index 33b01723a..a8ab5477a 100644
--- a/tests/all/js_globals/Array.rs
+++ b/tests/all/js_globals/Array.rs
@@ -796,3 +796,37 @@ fn find() {
         )
         .test()
 }
+
+#[test]
+fn map() {
+    project()
+        .file(
+            "src/lib.rs",
+            r#"
+                #![feature(proc_macro, wasm_custom_section)]
+
+                extern crate wasm_bindgen;
+                use wasm_bindgen::prelude::*;
+                use wasm_bindgen::js;
+                use JsValue;
+
+                #[wasm_bindgen]
+                pub fn array_map(array: &js::Array) -> js::Array {
+                    array.map(&mut |el, _, _| JsValue::from_f64(el.as_f64().unwrap().sqrt()))
+                }
+            "#,
+        )
+        .file(
+            "test.js",
+            r#"
+                import * as assert from "assert";
+                import * as wasm from "./out";
+
+                export function test() {
+                    const numbers = [1, 4, 9];
+                    assert.deepStrictEqual(wasm.array_map(numbers), [1, 2, 3]);
+                }
+            "#,
+        )
+        .test()
+}