Is your CSV file stored somewhere?  Or do you have it stored as a string?
To follow your structure, here is a plunker:
https://plnkr.co/edit/dCQ4HRz3mCTkjFYrkVVA?p=preview
var csv = 
`data1,data2,data3
col1,col2,col3`;
var lines = csv.split("\n");
while( typeof lines[0] !== "undefined" ){
    var line = lines.shift();
    var split = line.split(',');
    document.querySelector("#content").innerHTML += split[0]+"<br/>";
}
If you haven't got the CSV as a string, depending on if you are using Node to read a file or JavaScript in the browser to read an uploaded file, you need other code to convert that.  Or you may use a library.
You may have to handle trimming of spaces around commas by modifying the code above.
By the way, instead of creating temporary variables, some may prefer not using a while-loop:
https://plnkr.co/edit/31yMTw9RepdW1cF8I6qj?p=preview
document.querySelector("#content").innerHTML = 
csv.split("\n")        // these are lines
  .map(                // map those lines, 1 line to ...
    l => l.split(",")  // to 1 array
  ).map(
    a => a[0]+"<br/>"  // and map those arrays 1 array to the string
  ).join('');            // and join them to become 1 string
You may find those array manipulating functions interesting, like map(), filter(), reduce().
Hope these help!