用Java语言进行简单的数字输入验证（Firefox错误）

Question

function onlyNumberInput(evt) {
var theEvent = evt || window.event;
  var key = theEvent.keyCode || theEvent.which;
  key = String.fromCharCode( key );
  var regex = /[0-9]/;
  if( !regex.test(key) ) {
    theEvent.returnValue = false;
    if(theEvent.preventDefault) theEvent.preventDefault();
  }
}

Works fine on Chrome but in Firefox I cant press delete or backspace key to edit number. Where is the problem in my script? Of course I can use another way to do this but i want to know what errors is going on Firefox to execute above script?

Answer 1

if(theEvent.preventDefault) theEvent.preventDefault();

You missed " { "

if(theEvent.preventDefault){
  theEvent.preventDefault();
}

JavaScript is CaseSensitive. Remember that. Hope it helped. Good luck.

Answer 2

Hello @Raju Ahmed i check your code and figure that u are testing key's with regex but the problem is it's only checking for number's and this is what u asked. But also u need to check for Delete Key(which is 46) and also check for Backspace(which is 8) and other keys what u want to use.

Also i test your code on Chrome build 55.0.2883.87 m (64-bit) and it's also not working for delete, backspace and others.

You might want to use like this if u use jQuery:

function onlyNumberInput(evt) {
        var theEvent = evt || window.event;
        var allowed = [8, 17, 46, 37, 38, 39, 40];
        var key = theEvent.keyCode || theEvent.which;
        var regex = /[0-9]/;
        if($.inArray(allowed, key) !== -1) {
            key = String.fromCharCode( key );
            if( !regex.test(key) ) {
                theEvent.returnValue = false;
                if(theEvent.preventDefault) 
                    theEvent.preventDefault();
            }
        }
    }

If you want to use other keys, find the keyCode the key and add into allowed. If you don't use JQuery in your code please let me know. I can change it to normal version :)

One more thing this is allowed to use in JS if you have only one line job:

if(theEvent.preventDefault) 
    theEvent.preventDefault();

Edit II:

Well @Raju i have check the code again it's not working as u wish. So i found an example about it with a plugin if you want to use it.

Plugin : NumericInput,

Demo: Demo

You can check this link about number only input's: HTML Text Input allow only Numeric input