javascript - 检测 ctrl 键被按下或向上，keypress 事件不会触发

Question

I see some similar questions here (like JavaScript: Check if CTRL button was pressed ) but my problem is actually the event triggering. My js code:

    // Listen to keyboard. 
    window.onkeypress = listenToTheKey;
    window.onkeyup = listenToKeyUp;

    /*
        Gets the key pressed and send a request to the associated function
        @input key
    */
    function listenToTheKey(e)
    {
        if (editFlag == 0)
        {
            // If delete key is pressed calls delete
            if (e.keyCode == 46)
                deleteNode();

            // If insert key is pressed calls add blank
            if (e.keyCode == 45)
                createBlank();

            if (e.keyCode == 17)
                ctrlFlag = 1;
        }
    }

The event triggers for any other keys except the ctrl .
I need to also trigger it for ctrl .
I can't use jQuery/prototype/whatever so those solutions are not acceptable.

So... how can I detect the ctrl ?

Answer 1

Try using if (e.ctrlKey) .

MDN: event.ctrlKey

Answer 2

Using onkeydown rather than onkeypress may help.

From http://www.w3schools.com/jsref/event_onkeypress.asp

Note: The onkeypress event is not fired for all keys (eg ALT, CTRL, SHIFT, ESC) in all browsers. To detect only whether the user has pressed a key, use the onkeydown event instead, because it works for all keys.

Answer 3

Your event has a property named ctrlKey. You can check this to look if the key was pressed or not. See snippet below for more control like keys.

function detectspecialkeys(e){
    var evtobj=window.event? event : e
    if (evtobj.altKey || evtobj.ctrlKey || evtobj.shiftKey)
        alert("you pressed one of the 'Alt', 'Ctrl', or 'Shift' keys")
}
document.onkeypress=detectspecialkeys

Answer 4

This is basically Rick Hoving's answer, but it uses keydown like Danielle Cerisier suggests

 function detectspecialkeys(e) { var evtobj = window.event ? event : e if (evtobj.ctrlKey) console.log("You pressed ctrl") } document.onkeydown = detectspecialkeys

Please note that you may have to click inside the preview box to focus before pressing ctrl