三.跑马灯效果练习

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>跑马灯效果</title>
    <script src="../lib/vue-2.4.0.js"></script>
</head>
<body>
    <div id="app">
        <input type="button" value="启动" @click="_action">
        <input type="button" value="暂停" @click="_pause">
        <br>
        <h1 v-text="value"></h1>
    </div>

    <script>
        var vm=new Vue({
            el:"#app",
            data:{
                value:"1234567",
                intervalId:null,
            },
            methods:{
                _action(){
                    if(this.intervalId!=null)return;
                    //function里的this并不是指vm，要处理
                    var _this=this;
                    this.intervalId=setInterval(function(){
                        var start=_this.value.substring(1);
                        var end=_this.value.substring(0,1);
                        _this.value=start+end;
                    },500)
                    //或者采用箭头函数setInterval(()=>{解决this指向问题
               },
                _pause(){
                    clearInterval(this.intervalId);
                    this.intervalId=null;
                },
            }
        });
    </script>
</body>
</html>