Uncaught ReferenceError content is not defined

I am developing a website that show data that is retrieved from firebase database but I am getting the error here are the pics of my code and error

` firebase.initializeApp(firebaseConfig);

 var database = firebase.database();
 var re = database.ref('udetails');
 
 re.on('value', getData, errData);
 
 
 

function getData(data){
                
            var val = data.val();
            var ke = Object.keys(val);
            
            
        for(var i=0; i < ke.length; i++)
        {
            var k = ke[i];
            
            content +='<tr>';
            content += '<td>' + val[k].sr + '</td>';
            content += '<td>' + val[k].name + '</td>';
            content += '<td>' + val[k].mobile + '</td>';
            content += '<td>' + val[k].add + '</td>';
            content += '<td>' + val[k].email + '</td>';
            content += '<td>' + val[k].pass + '</td>';
            content += '<td>' + val[k].sregion + '</td>';
            content += '</tr>';
            
        $('#ex-table').append(content);
        
        }
}

function errData(err)
{
                console.log("error!");
                console.log(err);
}

`

This is the screenshot of error