add binding for join

tests/all/js_globals/Array.rs

@@ -76,4 +76,36 @@ fn last_index_of() {
             }
         "#)
         .test()
-}
+}
+
+#[test]
+fn join() {
+    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 join_array(this: &js::Array, delimiter: &str) -> String {
+                this.join(delimiter)
+            }
+
+        "#)
+        .file("test.ts", r#"
+            import * as assert from "assert";
+            import * as wasm from "./out";
+
+            export function test() {
+                let characters = ["a", "c", "x", "n"];
+                let stringValue = wasm.join_array(characters, ", ");
+
+                assert.equal("a, c, x, n", stringValue);
+                let withForwardSlash = wasm.join_array(characters, "/");
+                assert.equal("a/c/x/n", withForwardSlash);
+            }
+        "#)
+        .test()
+}