SOURCE

var child=Vue.extend({
	template:'#child',
	props:{
    max:{
      type:Number,
      default:5
    },
    min:{
      type:Number,
      default:1
    }
  },
  watch:{
    number(){
      console.log('触发自定义事件on-change传给父元素额参数是：'+this.number)
      this.$emit('on-change',this.number)
    }
  },
  methods: {
    fixNumber() {
      let fix;
      if(typeof  this.number==='string'){
        fix=Number(this.number.replace(/\D/g,''))
      }
      else{
        fix=this.number
      }
      if(fix>this.max || fix<this.min) {
        fix=this.min
      }
      this.number=fix
    },
    minus() {
      if(this.number<=this.min){
        return
      }
      this.number--
    },
    add() {
      if(this.number>=this.max){
        return
      }
      this.number++
    }
  },
  data() {
    return {
      number:this.min
    }
  }
});



let parent=new Vue({
	el:"#parent",
	data:{
		num:2
	},
	components:{
		'child':child
	},
	methods:{
		setNum(attr,val) {
		console.log(attr,val)
		  this[attr]=val
	  }
	}
})
		
		

		
<div id="parent">
	<p>
		父元素包含子组件
	</p>
	<child @on-change="setNum('num',$event)" :max='20' :min='2'></child>
	<p>
		父元素的属性num:{{num}}	
	</p>
</div>		
<!--组件模板-->
<template id="child">
	<div class="counter-component">
    <div class="counter-btn" @click="minus">-</div>
    <div class="counter-show">
      <input type="text" v-model="number" @keyup="fixNumber">
    </div>
    <div class="counter-btn" @click="add">+</div>
  </div>
</template>
		

.counter-component {
    position: relative;
    display: inline-block;
    overflow: hidden;
    vertical-align: middle;
  }
  .counter-show {
    float: left;
  }
  .counter-show input {
    border: none;
    border-top: 1px solid #e3e3e3;
    border-bottom: 1px solid #e3e3e3;
    height: 23px;
    line-height: 23px;
    width: 30px;
    outline: none;
    text-indent: 4px;
  }
  .counter-btn {
    border: 1px solid #e3e3e3;
    float: left;
    height: 25px;
    line-height: 25px;
    width: 25px;
    text-align: center;
    cursor: pointer;
  }
  .counter-btn:hover {
    border-color: #4fc08d;
    background: #4fc08d;
    color: #fff;
  }