<!DOCTYPE html> <html> <head> <meta charset="utf-8"> <meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1"> <title>Examples</title> <meta name="description" content=""> <meta name="keywords" content=""> <link href="" rel="stylesheet"> <script src="https://cdn.bootcss.com/vue/2.4.2/vue.min.js"></script> </head> <body> <div id="app"> <input type="text" v-model="items.text" ref="count"/> <div v-html="number"></div> </div> <script> new Vue({ el: \'#app\', data: { number: \'100\', items: { text:\'\', }, }, watch:{ //watch()监听某个值（双向绑定）的变化，从而达到change事件监听的效果 items:{ handler:function(){ var _this = this; var _sum = 5; //字体限制为100个 console.log(_this.$refs.count) _this.$refs.count.setAttribute("maxlength",_sum); _this.number= _sum- _this.$refs.count.value.length; }, deep:true } } }) </script> </body> </html>