We are creating a web user interface that looks like a desktop window. Now we need to handle the Alt key. When Alt key is pressed the focus goes to the upper menu.
In Javascript, how to get the event for Alt key when ONLY Alt key is pressed? I need to ensure that no other key was pressed at the same time.
Thanks in advance.
On all keyboards, the Alt key is located in the bottom row, directly to the left of the space bar.
The KeyboardEvent. altKey read-only property is a boolean value that indicates if the alt key ( Option or ⌥ on macOS) was pressed ( true ) or not ( false ) when the event occurred.
A KeyEventArgs, which specifies the key the user pressed and whether any modifier keys (CTRL, ALT, and SHIFT) were pressed at the same time, is passed with each KeyDown or KeyUp event.
The altKey property returns a Boolean value that indicates whether or not the "ALT" key was pressed when a key event was triggered.
maybe like this
document.onkeydown = keydown;
function keydown(evt) {
if (!evt) evt = event;
if (evt.altKey) {
console.log('alt');
}
} // function keydown(evt)
<input type"text" onkeydown="keydown" />
Working Demo
document.onkeyup = KeyCheck;
function KeyCheck(e)
{
var KeyID = (window.event) ? event.keyCode : e.keyCode;
switch(KeyID)
{
case 18:
document.Form1.KeyName.value = "Alt";
// do your work on alt key press....
break;
case 17:
document.Form1.KeyName.value = "Ctrl";
break;
}
}
And your html may be like that
<form name="Form1">
<input type="text" name="KeyName" value="" />
</form>
Note: If you want to get the alt event on other control/type than modify it with your requirements.
I don't know if this is the most elegant solution, but it worked fine.
$(function()
{
//Flag to check if another key was pressed with alt
var vAnotherKeyWasPressed = false;
//ALT keycode const
var ALT_CODE = 18;
//When some key is pressed
$(window).keydown(function(event)
{
//Identifies the key
var vKey = event.keyCode ? event.keyCode : event.which ? event.which : event.charCode;
//The last key pressed is alt or not?
vAnotherKeyWasPressed = vKey != ALT_CODE;
});
//When some key is left
$(window).keyup(function(event)
{
//Identifies the key
var vKey = event.keyCode ? event.keyCode : event.which ? event.which : event.charCode;
//If the key left is ALT and no other key is pressed at the same time...
if (!vAnotherKeyWasPressed && vKey == ALT_CODE)
{
//Focus the menu
$('#myMenu').focus();
//Stop the events for the key to avoid windows set the focus to the browser toolbar
return false;
}
});
});
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