Add JavaScript media type shortcut

README.md

@@ -46,6 +46,9 @@ Each type in the `types` array can be one of the following:
   `*/vnd+json` or `application/*+json`. The full mime type will be returned
   if matched.
 
+The JavaScript extensions `js` and `.js` match `application/javascript`,
+`application/x-javascript`, and `text/javascript`.
+
 Some examples to illustrate the inputs and returned value:
 
 ```js
@@ -98,6 +101,9 @@ Each type in the `types` array can be one of the following:
   `*/vnd+json` or `application/*+json`. The full mime type will be returned
   if matched.
 
+The JavaScript extensions `js` and `.js` match `application/javascript`,
+`application/x-javascript`, and `text/javascript`.
+
 Some examples to illustrate the inputs and returned value:
 
 ```js

src/index.spec.ts

@@ -166,6 +166,42 @@ describe("request(req, types)", () => {
       assert.strictEqual(request(req, ["multipart"]), "multipart");
     });
   });
+
+  describe("when Content-Type is JavaScript", () => {
+    it('should match "js"', () => {
+      assert.strictEqual(
+        request(createRequest("application/javascript"), ["js"]),
+        "js",
+      );
+      assert.strictEqual(
+        request(createRequest("application/x-javascript"), ["js"]),
+        "js",
+      );
+      assert.strictEqual(
+        request(createRequest("text/javascript"), ["js"]),
+        "js",
+      );
+      assert.strictEqual(
+        request(createRequest("application/json"), ["js"]),
+        false,
+      );
+    });
+
+    it('should match ".js"', () => {
+      assert.strictEqual(
+        request(createRequest("application/javascript"), [".js"]),
+        ".js",
+      );
+      assert.strictEqual(
+        request(createRequest("application/x-javascript"), [".js"]),
+        ".js",
+      );
+      assert.strictEqual(
+        request(createRequest("text/javascript"), [".js"]),
+        ".js",
+      );
+    });
+  });
 });
 
 describe("hasBody(req)", () => {
@@ -340,6 +376,21 @@ describe("is(mediaType, types)", () => {
       assert.strictEqual(is("multipart/form-data", ["multipart"]), "multipart");
     });
   });
+
+  describe("when media type is JavaScript", () => {
+    it('should match "js"', () => {
+      assert.strictEqual(is("application/javascript", ["js"]), "js");
+      assert.strictEqual(is("application/x-javascript", ["js"]), "js");
+      assert.strictEqual(is("text/javascript", ["js"]), "js");
+      assert.strictEqual(is("application/json", ["js"]), false);
+    });
+
+    it('should match ".js"', () => {
+      assert.strictEqual(is("application/javascript", [".js"]), ".js");
+      assert.strictEqual(is("application/x-javascript", [".js"]), ".js");
+      assert.strictEqual(is("text/javascript", [".js"]), ".js");
+    });
+  });
 });
 
 describe("match(expected, actual)", () => {

src/index.ts

@@ -9,6 +9,12 @@ import { parse } from "content-type";
 import { lookup } from "mime-types";
 import { test } from "media-typer";
 
+const JAVASCRIPT_MEDIA_TYPES = new Set([
+  "application/javascript",
+  "application/x-javascript",
+  "text/javascript",
+]);
+
 /**
  * Node.js HTTP request shape.
  */
@@ -58,7 +64,12 @@ export function is(
 
   for (const type of types) {
     const normalized = normalize(type);
-    if (match(normalized, val)) {
+    const extension = type.startsWith(".") ? type.slice(1) : type;
+
+    if (
+      (extension === "js" && JAVASCRIPT_MEDIA_TYPES.has(val)) ||
+      match(normalized, val)
+    ) {
       return type[0] === "+" || type.indexOf("*") !== -1 ? val : type;
     }
   }