Ctrl, Alt, Shift Keys
Question:
How do I detect mouse events with Ctrl, Alt, and Shift keys?
Answer: In modern browsers,
your script can check whether a mouse event occurred while the user was
pressing any of the Ctrl, Alt, Shift keys.
In the example below, this is accomplished for the
MouseDown
and
MouseUp events.
For other mouse events, a similar strategy may or may not work, depending on the browser.
To implement the Ctrl / Alt / Shift detection, you can use the
properties
event.ctrlKey,
event.altKey,
event.shiftKey
and the deprecated Navigator-specific property
event.modifiers.
Click anywhere on this page while pressing
any combination of Ctrl, Alt, and Shift keys,
and the key combination will be detected by the following script
(that resides in the <HEAD> section of the page).
Every time you click the mouse, you'll see the
event.ctrlKey,
event.altKey,
event.shiftKey or
event.modifiers
properties on the browser's status bar.
<script language="JavaScript">
<!--
function mouseDown(e) {
var ctrlPressed=0;
var altPressed=0;
var shiftPressed=0;
if (parseInt(navigator.appVersion)>3) {
var evt = navigator.appName=="Netscape" ? e:event;
if (navigator.appName=="Netscape" && parseInt(navigator.appVersion)==4) {
// NETSCAPE 4 CODE
var mString =(e.modifiers+32).toString(2).substring(3,6);
shiftPressed=(mString.charAt(0)=="1");
ctrlPressed =(mString.charAt(1)=="1");
altPressed =(mString.charAt(2)=="1");
self.status="modifiers="+e.modifiers+" ("+mString+")"
}
else {
// NEWER BROWSERS [CROSS-PLATFORM]
shiftPressed=evt.shiftKey;
altPressed =evt.altKey;
ctrlPressed =evt.ctrlKey;
self.status=""
+ "shiftKey="+shiftPressed
+", altKey=" +altPressed
+", ctrlKey=" +ctrlPressed
}
if (shiftPressed || altPressed || ctrlPressed)
alert ("Mouse clicked with the following keys:\n"
+ (shiftPressed ? "Shift ":"")
+ (altPressed ? "Alt " :"")
+ (ctrlPressed ? "Ctrl " :"")
)
}
return true;
}
if (parseInt(navigator.appVersion)>3) {
document.onmousedown = mouseDown;
if (navigator.appName=="Netscape")
document.captureEvents(Event.MOUSEDOWN);
}
//-->
</script>
The properties
event.ctrlKey,
event.altKey,
event.shiftKey
are self-explanatory. Their values are
true
if the corresponding keys are pressed, and
false
otherwise.
The Netscape 4 property
event.modifiers
is more tricky.
Depending on the actual key combination, this property has the following values:
Alt only modifiers=1 (001)
Ctrl only modifiers=2 (010)
Ctrl+Alt modifiers=3 (011)
Shift only modifiers=4 (100)
Shift+Alt modifiers=5 (101)
Shift+Ctrl modifiers=6 (110)
Shift+Alt+Ctrl modifiers=7 (111)
None of these keys modifiers=0 (000)
Thus, in the binary representation of the
event.modifiers
value:
the least significant (right) bit is 1 if Alt is pressed
the second bit is 1 if Ctrl is pressed
the third bit is 1 if Shift is pressed
JavaScripter.net.
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© 1999-2006, Alexei Kourbatov
