feat(js) Implement Number.new binding.

src/js.rs

@@ -367,6 +367,14 @@ extern {
 extern {
     pub type Number;
 
+    /// The `Number` JavaScript object is a wrapper object allowing
+    /// you to work with numerical values. A `Number` object is
+    /// created using the `Number()` constructor.
+    ///
+    /// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number
+    #[wasm_bindgen(constructor)]
+    pub fn new(value: JsValue) -> Number;
+
     /// The toLocaleString() method returns a string with a language sensitive
     /// representation of this number.
     ///

tests/all/js_globals/Number.rs

@@ -2,6 +2,32 @@
 
 use super::project;
 
+#[test]
+fn new() {
+    project()
+        .file("src/lib.rs", r#"
+            #![feature(proc_macro, wasm_custom_section)]
+
+            extern crate wasm_bindgen;
+            use wasm_bindgen::prelude::*;
+            use wasm_bindgen::js::Number;
+
+            #[wasm_bindgen]
+            pub fn new_number() -> Number {
+                Number::new(JsValue::from(42))
+            }
+        "#)
+        .file("test.ts", r#"
+            import * as assert from "assert";
+            import * as wasm from "./out";
+
+            export function test() {
+                assert.equal(typeof wasm.new_number(), "object");
+                assert.equal(wasm.new_number(), 42);
+            }
+        "#)
+        .test()
+}
 
 #[test]
 fn to_locale_string() {