javascript subtract(-) keycode

Question

ok, i need my code to check if minus/subtract/- was pressed, if it was pressed i want an alert box to pop. i tried with both 109 and 189 key codes but i still don't get the desired result. although i press "-" i don't get that alert box

Answer 1

Post some code. This works for me:

document.onkeydown = function (e) {
    if (e.keyCode === 109 || e.keyCode === 189) {
        alert('minus sign pressed');
    }
};

Full list of key codes here: http://www.cambiaresearch.com/c4/702b8cd1-e5b0-42e6-83ac-25f0306e3e25/Javascript-Char-Codes-Key-Codes.aspx

Answer 2

Don't do this in a keydown event handler - you put yourself at the mercy of different browsers' ideas about key codes and potential variation between key codes for different keyboard types. Do it in a keypress event and then you can get the character code instead, which is what you actually want.

document.onkeypress = function(evt) {
    evt = evt || window.event;
    var charCode = evt.which || evt.keyCode;
    var charStr = String.fromCharCode(charCode);
    if (charStr == "-") {
        alert("Minus!");
    }
};

All the information you could ever need about JavaScript key events: http://unixpapa.com/js/key.html

Answer 3

People are moving away from event.keyCode and event.charCode due to inconsistent implementations across browsers. Instead, use event.code. This is a string field.

Most browsers support Array.includes, so I tend to do the following:

if (['-', 'Minus', 'NumpadSubtract'].includes(e.code)) {
    // do something
}

Answer 4

You can discover keyCodes this way:

• Javascript Char Codes (Key Codes)
• Detecting keystrokes

Answer 5

The JavaScript charCodes, which you test for during a keypress event, are ASCII. 109 is the correct keyCode, if used in a keydown or keyup event.

"-" has a charCode of 45.

Answer 6

I hope this works for you, It detects users pressed keys and if it's the one your looking for it displays the alert, you may change the actual key to be any other key.

function detectSubstract(e)
{
var evtobj=window.event? event : e //distinguish between IE's explicit event object (window.event) and Firefox's implicit.
var unicode=evtobj.charCode? evtobj.charCode : evtobj.keyCode
var actualkey=String.fromCharCode(unicode)

    if (actualkey=="-")
    {
        alert('You pressed the minus key')
    }
}
document.onkeypress=detectSubstract