Provide a promise-based version of the API

README.md

@@ -89,6 +89,8 @@ this point that is the only option. You can do without the `options` altogether.
 
 The `cb` receives the typical `err` and `data` parameters.
 
+If no `cb` parameter is provided, the `fetch()` method instead returns a promise that will resolve with the expected data.
+
 ### Specifications
 
 Usage summary:

lib/index.js

@@ -37,19 +37,25 @@ function arrayify (obj) {
 function Ctx (ctx) {
     this.steps = ctx ? ctx.steps.concat([]) : [];
 }
-Ctx.prototype.fetch = function (options, cb) {
+Ctx.prototype.fetch = async function (options, cb) {
     if (typeof options === "function") {
         cb = options;
         options = {};
     }
+    let promise;
+    if (typeof cb !== "function") {
+        let resolve, reject;
+        promise = new Promise((res, rej) => { resolve = res; reject = rej;});
+        cb = (err, result) => { if (err) return reject(err); return resolve(result) ; } ;
+    }
+
     var url = exports.baseURL + this.steps.join("/")
     ,   embed = options && options.embed
     ,   request = makeRequest(url, embed)
     ,   type = this.type || "item"
     ,   key = this.linkKey
     ,   embedKey = embed ? "_embedded" : "_links"
     ;
-
     // what we want is to make one first request
     // if it has all the data, just return that
     // if not, then generate all the requests for each page, grab them all, collate the data, return that
@@ -86,6 +92,10 @@ Ctx.prototype.fetch = function (options, cb) {
             }
         );
     });
+    if (!!promise) {
+        return promise;
+    }
+
 };
 
 // generates a function for the root list

test/api.js

@@ -265,3 +265,11 @@ describe("Specification Series", function() {
         w3c.specificationseries(CSSCOLOR).specifications().fetch(listChecker(done, "CSS Color Module Level 3"));
     });
 });
+
+describe("Promises API", function() {
+    it('returns a promise if no callback is set', async function() {
+        const groups = await w3c.groups().fetch();
+        expect(groups).to.be.an("array");
+        expect(groups.some(function (it) { return it.title === "Cascading Style Sheets (CSS) Working Group"; })).to.be.ok();
+    });
+});