From a7deb69e80b44b16ce33a31c87e4c5172f69463b Mon Sep 17 00:00:00 2001
From: Tomohide Takao <amakunai.dorayaki@gmail.com>
Date: Thu, 12 Jul 2018 22:56:08 +0900
Subject: [PATCH] Bindings for Array.prototype.reduce(Right)

---
 src/js.rs                     | 14 ++++++++
 tests/all/js_globals/Array.rs | 66 +++++++++++++++++++++++++++++++++++
 2 files changed, 80 insertions(+)

diff --git a/src/js.rs b/src/js.rs
index fd6afa6c..33524bd2 100644
--- a/src/js.rs
+++ b/src/js.rs
@@ -240,6 +240,20 @@ extern "C" {
     #[wasm_bindgen(method)]
     pub fn push(this: &Array, value: JsValue) -> u32;
 
+    /// The reduce() method applies a function against an accumulator and each element in 
+    /// the array (from left to right) to reduce it to a single value.
+    /// 
+    /// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/Reduce
+    #[wasm_bindgen(method)]
+    pub fn reduce(this: &Array, predicate: &mut FnMut(JsValue, JsValue, u32, Array) -> JsValue, initial_value: JsValue) -> JsValue;
+
+    /// The reduceRight() method applies a function against an accumulator and each value 
+    /// of the array (from right-to-left) to reduce it to a single value.
+    /// 
+    /// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/ReduceRight
+    #[wasm_bindgen(method, js_name = reduceRight)]
+    pub fn reduce_right(this: &Array, predicate: &mut FnMut(JsValue, JsValue, u32, Array) -> JsValue, initial_value: JsValue) -> JsValue;
+
     /// The reverse() method reverses an array in place. The first array
     /// element becomes the last, and the last array element becomes the first.
     ///
diff --git a/tests/all/js_globals/Array.rs b/tests/all/js_globals/Array.rs
index a8ab5477..c9a0d55b 100644
--- a/tests/all/js_globals/Array.rs
+++ b/tests/all/js_globals/Array.rs
@@ -830,3 +830,69 @@ fn map() {
         )
         .test()
 }
+
+#[test]
+fn reduce() {
+    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_reduce(array: &js::Array) -> JsValue {
+                    array.reduce(&mut |ac, cr, _, _| JsValue::from_str(&format!("{}{}", &ac.as_string().unwrap(), &cr.as_string().unwrap().as_str())), JsValue::from_str(""))
+                }
+            "#,
+        )
+        .file(
+            "test.js",
+            r#"
+                import * as assert from "assert";
+                import * as wasm from "./out";
+
+                export function test() {
+                    assert.equal(wasm.array_reduce(['0', '1', '2', '3', '4']), '01234');
+                }
+            "#,
+        )
+        .test()
+}
+
+#[test]
+fn reduce_right() {
+    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_reduce_right(array: &js::Array) -> JsValue {
+                    array.reduce_right(&mut |ac, cr, _, _| JsValue::from_str(&format!("{}{}", &ac.as_string().unwrap(), &cr.as_string().unwrap().as_str())), JsValue::from_str(""))
+                }
+            "#,
+        )
+        .file(
+            "test.js",
+            r#"
+                import * as assert from "assert";
+                import * as wasm from "./out";
+
+                export function test() {
+                    assert.equal(wasm.array_reduce_right(['0', '1', '2', '3', '4']), '43210');
+                }
+            "#,
+        )
+        .test()
+}
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