Fix filtering by extension for js assets

tests/build.rs

@@ -331,7 +331,7 @@ fn it_builds_with_webpack_name_output() {
     build_creates_assets(&fixture, vec!["script.js"]);
 
     let out = fs::read_to_string(fixture.get_output_path().join("script.js")).unwrap();
-    assert!(out.contains(r#"//# sourceMappingURL=worker.js.map{"version":3,"file":"worker.js""#));
+    assert!(out.contains(r#"//# sourceMappingURL=worker.js.map"#));
 }
 
 #[test]

wranglerjs/index.js

@@ -16,7 +16,7 @@ function warn(...msg) {
 }
 
 function filterByExtension(ext) {
-  return v => v.indexOf("." + ext) !== -1;
+  return v => new RegExp(`.${ext}$`).test(v);
 }
 
 (async function() {