Add prev and next return values

README.md

@@ -54,6 +54,8 @@ Promise fulfilled with object having properties:
 * `limit` {Number} - Limit that was used
 * `[page]` {Number} - Only if specified or default `page`/`offset` values were used 
 * `[pages]` {Number} - Only if `page` specified or default `page`/`offset` values were used 
+* `[prev]` {Number} - Only if there is a previous page to go to.
+* `[next]` {Number} - Only if there is a next page to go to.
 * `[offset]` {Number} - Only if specified or default `page`/`offset` values were used
 
 ### Examples

index.js

@@ -75,6 +75,16 @@ function paginate(query, options, callback) {
     if (page !== undefined) {
       result.page = page;
       result.pages = Math.ceil(data.count / limit) || 1;
+      let prev = page - 1;
+      let next = page + 1;
+
+      if (prev > 0) {
+        result.prev = prev;
+      }
+
+      if (next <= result.pages) {
+        result.next = next;
+      }
     }
     if (typeof callback === 'function') {
       return callback(null, result);

tests/index.js

@@ -113,9 +113,35 @@ describe('mongoose-paginate', function() {
         expect(result.limit).to.equal(20);
         expect(result.page).to.equal(1);
         expect(result.pages).to.equal(5);
+        expect(result.next).to.equal(2);
+        expect(result.prev).to.be.undefined;
         expect(result).to.not.have.property('offset');
       });
     });
+    it('on the first page', function() {
+      return Book.paginate({}, { page: 1, limit: 20 }).then(function(result) {
+        expect(result.next).to.equal(2);
+        expect(result).to.not.have.property('prev');
+      });
+    });
+    it('on the last page', function() {
+      return Book.paginate({}, { page: 5, limit: 20 }).then(function(result) {
+        expect(result.prev).to.equal(4);
+        expect(result).to.not.have.property('next');
+      });
+    });
+    it('on the middle page', function() {
+      return Book.paginate({}, { page: 3, limit: 20 }).then(function(result) {
+        expect(result.prev).to.equal(2);
+        expect(result.next).to.equal(4);
+      });
+    });
+    it('with page 1 and limit', function() {
+      return Book.paginate({}, { page: 1, limit: 20 }).then(function(result) {
+        expect(result.next).to.equal(2);
+        expect(result).to.not.have.property('prev');
+      });
+    });
     it('with zero limit', function() {
       return Book.paginate({}, { page: 1, limit: 0 }).then(function(result) {
         expect(result.docs).to.have.length(0);