reactive stop watch based on vue

example.js

import stopwatch from 'vue-stopwatch'

stopwatch.$watch('seconds', console.log)

stopwatch.start()
//> 1
//> 2
//> 3

stopwatch.pause()
//> 

stopwatch.resume()
//> 4
//> 5

stopwatch.stop()
//> 

stopwatch.start()
//> 1
//> 2
//> ...

vue-stopwatch.js

import Vue from 'vue'

let ival, lastTs

export default new Vue({

    computed: {

        seconds () {
            return Math.round(this.milliseconds / 1000)
        }

    },

    data: {
        milliseconds: 0
    },

    methods: {

        pause () {
            clearInterval(ival)
        },

        resume () {
            this.start()
        },

        start () {
            lastTs = Date.now()
            ival = setInterval(() => {
                // get current timestamp
                const currentTs = Date.now()

                // get difference between now and last check
                const diff = currentTs - lastTs

                // add difference to total running time
                this.milliseconds += diff

                // save current timestamp for next iteration
                lastTs = currentTs
            }, 100)
        },

        stop () {
            this.milliseconds = 0
            clearInterval(ival)
        }

    }

})