HTML - Using pattern attribute - regex

Question

In html form, I need textarea which allows any type of text: numbers, symbols, newline or letters, including Hebrew letters. The only two rules:
The input must include the string: "{ser}"
The input should prohibit any use of "{" or "}" except for the above string
I tried this:
<form action="#">
...
<textarea pattern="[^\{\}]*\{ser\}[^\{\}]*" required>
האם אתה נמצא בשבת הקרובה? אם כן נא השב {ser} + שם מלא
</textarea>
...
<input type="submit" />
...
</form>
But for some reason it also allows sending texts that do not meet the rules. I would appreciate your help.

Answer 1

You cannot use pattern attribute on textareas, see the documentation.
maxlength specifies a maximum number of characters that the
is allowed to contain. You can also set a minimum length that is
considered valid using the minlength attribute, and specify that the
will not submit (and is invalid) if it is empty, using the
required attribute. This provides the with simple
validation, which is more basic than the other form elements (for
example, you can't provide specific regexs to validate the value
against using the pattern attribute, like you can with the input
element).
Perhaps implement a regex match with javascript?
function validateTextarea(text) {
var re = /ser/g;
var result = text.match(re);
if(result != null && result.length > 0)
// Do something
}
Then probably the best way is to check the function in onsubmit form attribute.