Jquery: filter input on keypress

Question

I have a text field, which will accept only the following characters:

Allowed characters: [a-z 0-9 + # - .]

This is the same filter SO

Answer 1

Thanks everyone.

Actually my problem was a little more difficult: filter invalid keys and start a ajax call for valid ones, in 2 different ways: if the user press SPACE/COMMA or while he/her still typing. Here's the code:

$(document).ready(function(){

$('#post_tags').keypress(function(e){
    var txt = String.fromCharCode(e.which);
    console.log(txt + ' : ' + e.which);

    if(txt.match(/^[^A-Za-z0-9+#\-\.]+$/))
    {
          return false;
    }
})

$('#post_tags').keyup(function(event){
      code = event.which
      var token = String.fromCharCode(code)
      var txt = $(this).val()

              //create a new tag, take it out of textfield
      if (code == 32 || code == 188)
      {
        console.log("AJAX new word keyup")

          $.ajax({
            type: 'get',
            url: '/posts/tags_change',
            dataType: "json",
            data: "query=" + $(this).val(),

            success: function(data) {
            console.log(data)
            $('#post_tags').val('')
            },

            error: function(data) {
                alert("Ajax error")
            }
          });
    }
    else
    {
                    //do autocomplete ajax
        console.log("typing:" + txt)
    }

});

})

Dont' know if this is 100% right!