var songs=new Vue({
  el:"#song",
  data:{
    songs:[
      {name:"A", singer: 'A', id:'a',checked:false},
      {name:"B", singer: 'B', id:'b',checked:false},
      {name:"C", singer: 'C', id:'c',checked:false},
      {name:"D", singer: 'D', id:'d',checked:false},
    ]
  },
  methods: {
      onMouseEnter: function (id) {
        console.log(id)
      },
      onMouseLeave: function () {
      
      }
  },
  computed:{
    selectAll:{
      get:function(){ return this.$data.songs.every(function(x){ return x.checked==true }) },
      set:function(checked){ this.$data.songs.map(function(x){x.checked=checked}) }
    }
  }
})