Download file using extjs4

I am working on an Extjs4 file upload control. I have a view with file upload control like -

Ext.define('Balaee.view.kp.dnycontent.Content', 
{
    extend:'Ext.form.Panel',
    requires:[
              'Balaee.view.kp.dnycontent.ContentView'
              ],
    id:'ContentId',
    alias:'widget.Content',
    enctype : 'multipart/form-data', 
    title:'This day in a history',
    items:[

    {
        xtype: 'fileuploadfield',
        hideLabel: true,
        emptyText: 'Select a file to upload...',
        //inputType: 'file',
        id: 'upfile',
        width: 220
}],
   buttons: [{
        xtype : 'button',
        fieldlabel:'upload',
        action:'upload',
        name:'upload',
        text: 'Upload',
        formBind:'true'

    }]
});

And the corresponding action in the controller is

getUpload : function() {

        var file10 = Ext.getCmp('ContentId').getEl().down('input[type=file]').dom.files[0];

        var reader = new FileReader();
        reader.onload = function(oFREvent) {
            fileobj=oFREvent.target.result;
            console.log(oFREvent.target.result);

        };
        }
    });

Thus, the controller function returns the downloaded file and displays it in encoded format inside the built-in read function. that is, "console.log (oFREvent.target.result);" the line displays the downloaded file data in encoded format in the console. I need to send this file to the server. So I go above fileobj as a parameter to store as -

var storeObj=this.getStore('kp.DnycontentStore');
         storeObj.load({
         params:{
         data:fileobj
         },
         callback: function(records,operation,success){
           console.log("send");
         },
         scope:this
         })

fileobj undefined reader.onload. , ? . , - .