[update] add increase function

Author: toxic-johann

.travis.yml

@@ -0,0 +1,18 @@
+language: node_js
+node_js:
+    - '9'
+    - '8'
+    - '6'
+script:
+    - 'npm test'
+after_success:
+    - 'npm install coveralls && npm install nyc && ./node_modules/.bin/nyc report --temp-directory=coverage --reporter=text-lcov | ./node_modules/.bin/coveralls'
+notifications:
+    webhooks:
+        urls:
+            - 'https://www.travisbuddy.com/'
+        on_success: never
+        on_failure: always
+        on_start: never
+        on_cancel: never
+        on_error: never

__tests__/index.js

@@ -78,4 +78,13 @@ describe('base test', () => {
       expect(() => helper.getLatest(123)).toThrow('prefix must be RegExp or String, but not number');
     });
   });
+
+  describe('increase', () => {
+    test('normal use', () => {
+      expect(helper.increase('dev-v')).toBe('0.1.4');
+      expect(helper.increase('dev-v', 'minor')).toBe('0.2.0');
+      expect(helper.increase('dev-v', 'major')).toBe('1.0.0');
+      expect(helper.increase()).toBe(null);
+    });
+  });
 });

index.js

@@ -91,6 +91,11 @@ class Helper {
 
     return obj.version;
   }
+
+  increase(prefix = '', type = 'patch') {
+    const latest_semver = this.getLatest(prefix, { semver: true });
+    return semver.inc(latest_semver, type);
+  }
 }
 
 module.exports = new Helper();