vue upload上传文件限制文件类型

beforeFileUpload(file,fileList){

      let fileName = file.name;

      let uid = file.uid

      let pos = fileName.lastIndexOf(".");

      let lastName = fileName.substring(pos, fileName.length);

      console.log(lastName,lastName.toLowerCase());

      if (

        lastName.toLowerCase() !== ".pdf" &&

        lastName.toLowerCase() !== ".doc"&&

        lastName.toLowerCase() !== ".docx"&&

        lastName.toLowerCase() !== ".zip"&&

        lastName.toLowerCase() !== ".rar"&&

        lastName.toLowerCase() !== ".xls"&&

        lastName.toLowerCase() !== ".xlsx"

      ) {

        this.$message.error("文件必须为.pdf .doc .docx .zip .rar .xls .xlsx类型");

        this.$refs.uploadFile.clearFiles();

        return false;

      }

    },