file文件转换为二进制数据

?

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

const beforeUpload = file => {         var reader = new FileReader();       reader.readAsDataURL(file);       //转化二进制流，异步方法       reader.onload = function(){         //完成后this.result为二进制流         console.log(this.result,"0-00-");         var base64Str = this.result;         var startNum = base64Str.indexOf("base64,");         startNum = startNum*1 + 7;         //去除前部格式信息（如果有需求）         var baseStr = base64Str.slice(startNum);         console.log(baseStr,"二进制数据！！！")       }  }