Added WeakSet has method

src/js.rs

@@ -628,6 +628,12 @@ extern {
     /// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/WeakSet
     #[wasm_bindgen(constructor)]
     pub fn new() -> WeakSet;
+
+    /// The has() method returns a boolean indicating whether an object exists in a WeakSet or not.
+    /// 
+    /// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/WeakSet/has
+    #[wasm_bindgen(method)]
+    pub fn has(this: &WeakSet, value: Object) -> bool;
 }
 
 // JsString

tests/all/js_globals/WeakSet.rs

@@ -27,3 +27,35 @@ fn new() {
         "#)
         .test()
 }
+
+#[test]
+fn has() {
+    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 has_value(this: &js::WeakSet, value: js::Object) -> bool {
+                this.has(value)
+            }
+        "#)
+        .file("test.ts", r#"
+            import * as assert from "assert";
+            import * as wasm from "./out";
+
+            export function test() {
+                let set = new WeakSet();
+                let value = {some: "value"};
+                set.add(value);
+                assert.equal(wasm.has_value(set, value), true);
+
+                let nonex = {nonexistent: "value"};
+                assert.equal(wasm.has_value(set, nonex), false);
+            }
+        "#)
+        .test()
+}