my blog writing input is removing last line in react

this is the current state where I have 4 lines and 5th line in current input

and this is my react code

import { FC, useEffect, useState } from "react";

interface BlogWitterProps {}

const BlogWitter: FC<BlogWitterProps> = ({}) => {
  const [markdownContent, setMarkdownContent] = useState("");
  const [currentLine, setCurrentLine] = useState("");

  // on each new line, update the markdown content

  useEffect(() => {
    console.log("markdownContent", markdownContent);
    console.log("currentLine", currentLine);
  }, [currentLine, markdownContent]);

  const handleKeyDown = (e: React.KeyboardEvent<HTMLInputElement>) => {
    if (e.key === "Enter") {
      setMarkdownContent((prev) => {
        return prev + currentLine + "n";
      });
      setCurrentLine("");
    } else if (e.key === "Backspace" && currentLine === "") {
      e.preventDefault();
      setMarkdownContent((prev) => {
        const lines = prev.split("n");
        const lastLine = lines.pop();
        console.log("lines", lines);

        setTimeout(() => {
          // If the last line is not empty, update the current line state
          if (lastLine !== "") {
            setCurrentLine(lastLine + "n");
          } else {
            setCurrentLine("");
          }
        }, 0);

        return lines.join("n");
      });
    }
  };

  return (
    <div className="">
      <div>
        {markdownContent.split("n").map((line, index) => {
          return (
            <div key={index}>
              {line}
              <br />
            </div>
          );
        })}
      </div>
      <input
        value={currentLine}
        onChange={(e) => {
          setCurrentLine(e.target.value);
        }}
        className="w-full resize-none outline-none text-2xl bg-transparent border border-black"
        onKeyDown={handleKeyDown}
      />
    </div>
  );
};

export default BlogWitter;

so if I press backspace and it takes me to last line to edit then press anter again without changing anything it is remove the last line’s new line and gives me this

I am trying to get it to work as in medieum where you can edit each line seperatly