vue中选择图片，预览图片，返回base64

1.html内容

<el-col :span="20" style="margin-left: 100px;">
    <input type="file" name="avatar" accept="image/gif,image/jpeg,image/jpg,image/png" @change="changeCoverImg($event)">
    <img :src="coverImg">
</el-col>

2.data中声明变量

　　coverImg:'',

3.methods中方法

changeCoverImg:function(e) {
    var file = e.target.files[0]
    var reader = new FileReader()
    var that = this
    reader.readAsDataURL(file)
    reader.onload = function(e) {
        that.coverImg = this.result
        // console.log(that.coverImg)
    }
},
4.效果图

 返回的base64：