learnin-some-vue/app.js

var app = new Vue({
  el: '#app',
  data: {
    counter: 0,
    x: 0,
    y: 0,
  },
  methods:{
    increase(step, event){
      this.counter+= step;
    },
    updateCoordinates(event){
      this.x = event.clientX;
      this.y = event.clientY;
    }
  }
})