Return Promise when no callback is supplied

README.md

@@ -32,13 +32,17 @@ kmeans.clusterize(vectors, {k: 4}, (err,res) => {
   if (err) console.error(err);
   else console.log('%o',res);
 });
+
+// Example with promise
+await const res = kmeans.clusterize(vectors, {k: 4});
+console.log('%o',res);
 ```
 ## Inputs
  - **vectors** is a nXm array (n [lines] : number of points, m [columns] : number of dimensions)
  - **options** object:
     - **k** : number of clusters
     - **distance** (optional) : custom distance function returning the distance between two points `(a,b) => number`, *default* Euclidian Distance
- - **callback** node-style callback taking error and result argument
+ - **callback** (optional) node-style callback taking error and result argument. If not supplied, the function returns a promise with the result.
 
 ## Outputs
 An array of objects (one for each cluster) with the following properties:

lib/kmeans.js

@@ -231,6 +231,21 @@ class Clusterize {
 }
 
 exports.clusterize = (vector, options, callback) => {
+  if (!options || !vector) {
+    throw new Error('Provide 2 arguments: vector, options');
+  }
+
+  if (vector && options && !callback) {
+    return new Promise((resolve, reject) => {
+      /* eslint-disable no-new */
+      new Clusterize(vector, options, (err, data) => {
+        if (err !== null) {
+          return reject(err);
+        }
+        return resolve(data);
+      });
+    });
+  }
   return new Clusterize(vector, options, callback);
 };
 

test/index.js

@@ -30,20 +30,30 @@ const data3D = [
  * Tests
  */
 describe('kmeans', () => {
+  describe('#clusterize()', () => {
+    it('should return a promise if no callback function', () => {
+      /* eslint-disable new-cap */
+      kmeans.clusterize([], {}).should.be.Promise();
+    });
+  });
+
   describe('#clusterize() errors', () => {
-    it('should throw an error if there aren\'t 3 arguments', () => {
+    it('should throw an error if there aren\'t 2 arguments', () => {
       (() => {
         kmeans.clusterize();
-      }).should.throw('Provide 3 arguments: vector, options, callback');
+      }).should.throw('Provide 2 arguments: vector, options');
       (() => {
         kmeans.clusterize({});
-      }).should.throw('Provide 3 arguments: vector, options, callback');
+      }).should.throw('Provide 2 arguments: vector, options');
+    });
+
+    it('should not throw an error if there are 2 arguments', () => {
       (() => {
         kmeans.clusterize({}, {});
-      }).should.throw('Provide 3 arguments: vector, options, callback');
+      }).should.not.throw();
     });
 
-    it('should throw an error if no callback function', () => {
+    it('should throw an error if callback is no function', () => {
       (() => {
         kmeans.clusterize([], {}, {});
       }).should.throw('Provide a callback function');
@@ -57,6 +67,10 @@ describe('kmeans', () => {
       });
     });
 
+    it('should reject promise if no \'k\' option', () => {
+      kmeans.clusterize({}, { k: 3 }).should.be.rejected();
+    });
+
     it('should return an error if the data vector is not an array', done => {
       kmeans.clusterize({}, { k: 3 }, (err, res) => {
         should.not.exist(res);
@@ -85,6 +99,10 @@ describe('kmeans', () => {
       });
     });
 
+    it('should return a result (array) with promise', () => {
+      kmeans.clusterize(data3D, { k: 3 }).should.be.eventually.have.length(3);
+    });
+
     it('should return 2 groups with the 2 vectors', done => {
       kmeans.clusterize([[1, 1], [2, 2]], { k: 2 }, (err, res) => {
         should.not.exist(err);