Add binding for String.prototype.toLowerCase

src/js.rs

@@ -1065,6 +1065,13 @@ extern "C" {
     #[wasm_bindgen(method, js_class = "String")]
     pub fn substr(this: &JsString, start: i32, length: i32) -> JsString;
 
+    /// The toLowerCase() method returns the calling string value
+    /// converted to lower case.
+    ///
+    /// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/toLowerCase
+    #[wasm_bindgen(method, js_class = "String", js_name = toLowerCase)]
+    pub fn to_lower_case(this: &JsString) -> JsString;
+
     /// The toString() method returns a string representing the specified object.
     ///
     /// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/toString

tests/all/js_globals/JsString.rs

@@ -396,6 +396,32 @@ fn substr() {
         .test()
 }
 
+#[test]
+fn to_lower_case() {
+    project()
+        .file("src/lib.rs", r#"
+            #![feature(proc_macro, wasm_custom_section)]
+
+            extern crate wasm_bindgen;
+            use wasm_bindgen::prelude::*;
+            use wasm_bindgen::js;
+
+            #[wasm_bindgen]
+            pub fn string_to_lower_case(this: &js::JsString) -> js::JsString {
+                this.to_lower_case()
+            }
+        "#)
+        .file("test.ts", r#"
+            import * as assert from "assert";
+            import * as wasm from "./out";
+
+            export function test() {
+                assert.equal(wasm.string_to_lower_case("Mozilla"), "mozilla");
+            }
+        "#)
+        .test()
+}
+
 #[test]
 fn to_string() {
     project()