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Asked: 2020-05-20 07:36:06 +0800 CST 2020-05-20 07:36:06 +0800 CST

How to validate special characters in a text field

  • 772

The problem I have is that I need to validate a text field so that it only accepts me ";"and "_". So far it doesn't work for me with the code I have.

Code:

 function doNotSubmitFormOnEnterPress(event) {
    if (event.keyCode === 188 ) {
           return false;
    }
    return true;
 }
javascript

2 Answers

  1. Best Answer

    You can do this with Jquery , You can validate if the Shift key is pressed , with the property shiftKey , it will return a boolean value if the key is pressed or not

    $('#valor').keydown(function(e) {
   if(e.shiftKey && e.keyCode ===188|| e.shiftKey && e.keyCode ===189)
     return true;
   if (e.key.length == 1) 
        return false
});
    <script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<input type="text"  id="valor" >

    • 5

  2. I suggest using keypressinstead of keyDownso it doesn't limit actuation of ctrl keys , such as: Backspace, Delete, Etc. Although I lean toward using jQuery as well, I instead show for illustrative purposes the use of addEventListener() to handle the event onKeyPressassociated to the <input>, as well as the use of event.preventDefault() , to prevent the normal flow of the <input>in case of not typing the required values.

    Example:

    document.getElementById("name").addEventListener("keypress", doNotSubmitFormOnEnterPress);

function doNotSubmitFormOnEnterPress(event) {
 if(";_".indexOf(event.key) == -1){ // colocar la cadena de caracteres permitidos
  event.preventDefault();
 };
};
    <input id="name">

    • 2