javascript - Define allowed characters in text objects HTML -

Anyway, can I define encoding in text areas using HTML and Pure JS?
I do not want them to allow special Unicode characters (like ♣ ♦ ♠).
Valid character range (for my purpose) Unicode code point U + 0000 to U + 00FF .
It is okay to transfer accurate words with empty string on form submissions (without warning to user).

So, as you have explained in your comments: you want to replace those characters, Who regardless of the warning on form-submission with invalid string invalid.

The following example html (body content):

  & lt; Form action = "demo_form.asp" & gt; First name: & lt; Input type = "text" name = "fname" /> & Lt; Br> Last name: & lt; Input type = "text" name = "lname" /> & Lt; Br> Likes: & lt; Textarea name = "txt_a" & gt; & Lt; / Textarea & gt; & Lt; Br> What she Dislikes: & lt; Textarea name = "txt_b" & gt; & Lt; / Textarea & gt; & Lt; Br> & Lt; Input type = "submit" value = "submit" & gt; & Lt; / Form & gt;  

Here is a basic concept javascript:

  function demo () {for (var elms = this.getElementsByTagName ('textarea'), l = ams .length; L -; Elmas [L] .value = elms [L] .value.replace (/ [^ \ u0000- \ u00FF] / g, '')); } Window.onload = function () {document.forms [0] .onubmit = Demo; // Use any method of choice on the onsubmit of the hook form;  

The basic idea is to emphasize the browser's Regex engine to match on Unicode (local charset) using \ uXXXX notation.
Then we only limit one: [\ u0000- \ u00FF] and finally we specify that <^> [^ \ u0000- \ U00FF] .
All the items that match those criteria will be replaced with form code (submission) on

'' . No warning. - You can extend this concept independently to include in your code (the way your code-flow fits) (and where it is needed, give it to input type = "text"

Edit:
Note that your current is valid - category specifications ( \ u0000- \ u00FF ) are all special types of 'Pesky' Effectively reject special characters:

• Fancy quote '' ""
• € However, it is perfectly well done with full C1 control.

-Block (), on the other hand .. It is in line with the inclusion of the complete C-control block. Effectively, it is now valid for your (which you have requested) valid four-set:

As you can see now, this is too much for this reason that sensible applications (ultimately) Unicode (usually encoded for the web in the form of UTF-8) Yoga is starting to begin and the users who provide (only (obviously clearly) reasons to accept)
^{Most Common Verification Question (Real World To validate the concept is nothing more than the example of high-school-class (and even more: regularly with examples that can be easily understood to explain the basics Name of the expression, such as name / email / Address) apply some official identification system (passport etc.) for the regrettable that people's names, addresses etc. In fact: Even the absolute current Unicode names each person (in original writing) on ​​the planet (that's actually still alive) !! Real world example: When your boarding pass has different certificates, try leaving the commercial flight and leaving it, then your passport (whatever is wrong). 'Just' missing an umlaut is a problem, somewhere bad situation, imagine a woman with a German name, Thai married a man with last name and a masculine last name ..}

End: Please feel that Most of the cases This is completely useless (if you silently do without any warning) because:
You never can simply accept user input on the server - without proper cleaning In the party , so you are already cleaning your input on that form (without knowing the user) on a form that you forget to think of users with a newbie programmer (Javascript (For example), it sometimes seems to repeat the work done in Javascript already on the client-side) ... Typically , replicating th Server-side vendor on client-side (Usually using Javascript), the user dynamically knows how the server will not be allowed (by sending the data back and forth) and accordingly customize it!