Added .toHeaders() function (#9)

Author: MarcusLongmuir

README.md

@@ -83,6 +83,10 @@ Otherwise:
 #### .appendFromString(str: string): void
 Appends the headers defined in the provided CLRF-delimited string (e.g. `key-a: one\r\nkey-b: two`)
 
+#### .toHeaders(): Headers
+Returns an instance of the browser's `Headers` class. This will throw an exception if the current browser does not have
+the `Headers` class.
+
 ## Warning about `.append` in native `Headers`
 The `.append` function of the `Headers` class differs significantly between browsers.
 

package.json

@@ -1,6 +1,6 @@
 {
   "name": "browser-headers",
-  "version": "0.1.7",
+  "version": "0.2.0",
   "main": "lib/index.js",
   "types": "lib/index.d.ts",
   "repository": "https://github.com/improbable-eng/js-browser-headers",

src/BrowserHeaders.ts

@@ -19,17 +19,14 @@ interface MapConstructor {
 
 declare const Map: MapConstructor;
 
-export type HeaderObject = {[key: string]: string|string[]};
-export type HeaderMap = Map<string, string|string[]>;
-
 // Declare that there is a global property named "Headers" - this might not be present at runtime
 declare const Headers: any;
 
 // BrowserHeaders is a wrapper class for Headers
-export default class BrowserHeaders {
+export class BrowserHeaders {
   keyValueMap: {[key: string]: string[]};
 
-  constructor(init: HeaderObject | HeaderMap | BrowserHeaders | WindowHeaders | string = "", options: {splitValues: boolean} = { splitValues: false } ) {
+  constructor(init: BrowserHeaders.ConstructorArg = {}, options: {splitValues: boolean} = { splitValues: false } ) {
     this.keyValueMap = {};
 
     if (init) {
@@ -46,19 +43,19 @@ export default class BrowserHeaders {
           });
         });
       } else if (init instanceof BrowserHeaders) {
-        init.forEach((key, values) => {
+        (init as BrowserHeaders).forEach((key, values) => {
           this.append(key, values)
         });
       } else if (typeof Map !== "undefined" && init instanceof Map) {
-        const asMap = init as HeaderMap;
+        const asMap = init as BrowserHeaders.HeaderMap;
         asMap.forEach((value: string|string[], key: string) => {
           this.append(key, value);
         });
       } else if (typeof init === "string") {
         this.appendFromString(init);
       } else if (typeof init === "object") {
         Object.getOwnPropertyNames(init).forEach(key => {
-          const asObject = init as HeaderObject;
+          const asObject = init as BrowserHeaders.HeaderObject;
           const values = asObject[key];
           if (Array.isArray(values)) {
             values.forEach(value => {
@@ -162,4 +159,22 @@ export default class BrowserHeaders {
         callback(key, this.keyValueMap[key]);
       }, this);
   }
+  
+  toHeaders(): WindowHeaders {
+    const headers: WindowHeaders = new Headers();
+    
+    this.forEach((key, values) => {
+      values.forEach(value => {
+        headers.append(key, value);
+      });
+    });
+    
+    return headers;
+  }
+}
+
+export namespace BrowserHeaders {
+  export type HeaderObject = {[key: string]: string|string[]};
+  export type HeaderMap = Map<string, string|string[]>;
+  export type ConstructorArg = HeaderObject | HeaderMap | BrowserHeaders | WindowHeaders | string;
 }

src/index.ts

@@ -1,3 +1 @@
-import BrowserHeaders from "./BrowserHeaders";
-
-export default BrowserHeaders;
+export { BrowserHeaders } from "./BrowserHeaders";

test/BrowserHeaders.spec.ts

@@ -1,6 +1,7 @@
-import BrowserHeaders from "../src/BrowserHeaders";
+import { BrowserHeaders } from "../src/BrowserHeaders";
+import { getHeaderValues } from "../src/util";
 
-const { deepEqual } = require("assert");
+const { deepEqual, ok } = require("assert");
 
 declare function describe(name: string, test: () => void): void;
 declare function it(name: string, test: () => void): void;
@@ -201,7 +202,7 @@ describe("browser-headers", () => {
       browserHeaders.append("keyA", ["one", "Two"]);
       browserHeaders.append("keyB", ["three", "four"]);
       const visited: string[] = [];
-      browserHeaders.forEach((key, values) => {
+      browserHeaders.forEach((key: string, values: string[]) => {
         visited.push(key + "." + values.join(","));
       });
       deepEqual(visited, [
@@ -256,6 +257,25 @@ describe("browser-headers", () => {
         deepEqual(browserHeaders.get("keyA"), ["one", "Two"]);
         deepEqual(browserHeaders.get("keyB"), ["three"]);
       });
+
+      describe("toHeaders", () => {
+        it("should return a Headers instance that contains the same headers", () => {
+          const browserHeaders = new BrowserHeaders({
+            "keyA": ["one", "Two"],
+            "keyB": "three"
+          });
+          const headers = browserHeaders.toHeaders();
+          const keyA = getHeaderValues(headers, "keyA");
+
+          // The value of keyA is one of ["one", "Two"], ["one,Two"] or ["one, Two"] depending on whether or not the
+          // `.append` function of the current browser's Header class concatenates and what it joins by.
+
+          // Join the array by ", " so that the value(s) should now be either separated by ", " or just ","
+          const keyAString = keyA.join(", ");
+          ok(keyAString === "one, Two" || keyAString === "one,Two");
+          deepEqual(getHeaderValues(headers, "keyB"), ["three"]);
+        });
+      });
     });
   }