update text area using jquery

First of all, @epascarello is correct in stating that you need to escape all data going into your database. You are also doing it in an extremely unsafe way, guaranteed to be hacked. Creating your SQL-statements that way opens your code up for something called SQL Injection, and is probably the most common way a website is hacked.

You need to use prepared statements and safeguard your code saving the data, as well as encode the data going in.

As per the examples in this guide and the explanations given there, PDO is the only safe way to handle user input that is being saved to a database. This is because of the way the prepared statements are prepared on the database server, before you put your data into the query.

As for code, look at this for saving the data:

$host = 'localhost';
$db   = 'myDatabase';
$username = 'awesomeUser';
$pass = 'someTotallySecretPassword';
$charset = 'utf8';

$dsn = "mysql:host=$host;dbname=$db;charset=$charset";

$opt = [ PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_ASSOC];

$pdo = new PDO($dsn, $username, $password, $opt);
$stmt = $pdo->prepare('INSERT INTO news SET title = :title, details = :details, date = :date');
$stmt->execute([
    'title' => urlencode($_POST["newsTitle"]), 
    'details' => urlencode($_POST["newsDetails"]),
    'date' => $_POST["newsDate"]
]);
$user = $stmt->fetch();

I am going to advice you to also create the date yourself, on the server, either in SQL or in PHP, unless your use case needs the user to be able to insert a date different than the creation time of the news-article you are creating. If the user does have a need to insert an arbitrary date, you need to do some validation on that as well, to make sure it is valid.

Now, when you need to get the data out again, you need to decode the data from the database with javascript:

function decode(text)
{
    return decodeURIComponent(text.replace(/\+/g,' '));
}

function upd(title,detail,date,id)
{
  $("#newsTitle").val( decode(title) );
  $("#newsDetails").val( decode(detail) );
  $("#newsDate").val( date );
  $("#id").val( id );
}

You can prevent the default action of pressing enter in the textarea with an event listener.

<textarea placeholder="You can not press enter"></textarea>
<script>
document.querySelector("textarea").addEventListener("keypress", function(e){
  if(e.keyCode==13){
    e.preventDefault();
  }
});
</script>

On the server-side, with PHP, you should replace all the line breaks with an empty String so the insertion will not fail (from this answer).

str_replace("\r\n", "", "your insertion statement string");