I want to prevent number input on keydown event on textfield and run custom handler function. Here are the issues
e.target.value
is useless since the key value is not projected into the target value yete.keyCode
for number depends on keyboard type, language layout, Fn or Shift keyString.fromCharCode(e.keyCode)
is not reliable, at least on my keyboard (Czech qwerty)e.keyCode
is a legacy attribute and suggests e.char
instead, but it is not implemented in browsers yetSo how to catch the number input before it appears in the textfield?
You could use the key
property of the keydown
event:
document.getElementById("i").addEventListener("keydown", function(evt) {
if (/^\d$/.test(evt.key)) {
evt.preventDefault();
}
});
<input id="i">
Use the keypress
event instead. It's the only key event which will give you information about the character that was typed, via the which
property in most browsers and (confusingly) the keyCode
property in IE. Using that, you can conditionally suppress the keypress
event based on the character typed. However, this will not help you prevent the user from pasting or dragging in text containing numeric characters, so you will still need some kind of extra validation.
My favourite reference for JavaScript key events: http://unixpapa.com/js/key.html
textBox.onkeypress = function(e) {
e = e || window.event;
var charCode = (typeof e.which == "undefined") ? e.keyCode : e.which;
var charStr = String.fromCharCode(charCode);
if (/\d/.test(charStr)) {
return false;
}
};