feat(diff valueOf): diff valueOf

src/index.js

@@ -47,9 +47,13 @@ class Dayjs {
   }
 
   unix() {
+    return Math.floor(this.valueOf() / 1000)
+  }
+
+  valueOf() {
     // timezone(hour) * 60 * 60 * 1000 => ms
     const zonePad = !this.utc ? 0 : this.timeZone * 60 * 60 * 1000
-    return Math.floor((this.$date.getTime() + zonePad) / 1000)
+    return this.$date.getTime() + zonePad
   }
 
   toString() {
@@ -139,6 +143,11 @@ class Dayjs {
       }
     })
   }
+
+  diff(otherDate) {
+    const other = otherDate instanceof Dayjs ? otherDate : new Dayjs(otherDate)
+    return this.valueOf() - other.valueOf()
+  }
 }
 
 export default config => (

test/display.test.js

@@ -50,3 +50,22 @@ test('Format Complex with other string - : / ', () => {
   expect(dayjs().format(string)).toBe(moment().format(string))
 })
 
+it('Difference', () => {
+  const dateString = '20110101'
+
+  const dayjsA = dayjs()
+  const dayjsB = dayjs(dateString)
+
+  const momentA = moment()
+  const momentB = moment(dateString)
+  expect(dayjsA.diff(dayjsB)).toBe(momentA.diff(momentB))
+})
+
+it('Unix Timestamp (milliseconds)  ', () => {
+  expect(dayjs().valueOf()).toBe(moment().valueOf())
+})
+
+it('Unix Timestamp (seconds)  ', () => {
+  expect(dayjs().unix()).toBe(moment().unix())
+})
+