Javascript var data=allTextLines[i].split（'，'）；字符串=数据[i]+'，'；}output.value=string；}）；}显示的输出未定义 <textarea id="recipients" name="recipient

var data=allTextLines[i].split（'，'）；字符串=数据[i]+'，'；}output.value=string；}）；}显示的输出未定义

<textarea id="recipients" name="recipients" class="form-control"></textarea>
<input name="file" type="file" id="files" class="form-control" value=""> 
<a id="fetch_number" class="btn btn-primary btn-sm" href="">pull text file</a>

$(document).ready(function() {
   $('#fetch_number').on('click', function() {
      var files = document.getElementById('files').files;
      if (!files.length) {
         alert('Please select a file!');
         return;
      }   

      if (window.File && window.FileReader && window.FileList && window.Blob) {
         var text_file = document.getElementById('files');
         var files = text_file.files;

         var file = files[0];
         var extension = file.name.split('.').pop();
         var start = 0;
         var stop = file.size - 1;

         var reader = new FileReader();
         reader.onload = function(e){
                var output = e.target.result;
                output = output.split("/\r\n|\n/");
                var string = '';
                for (var i=0; i < output.length; i++) {
                   var data = allTextLines[i].split(',');
                   string = data[1] + ',';
                }   

               return string;

              $("#recipients").text(string);
         };

      } else {
            alert('The File APIs are not fully supported by your browser.');
    }
 });
});