How to fire a keyboard shortcut function in JavaScript?

Question

I have a record functionality in my website. If a user hits Ctrl + Alt + R the recording will begin. Now I would like a button named RECORD in my html page, so that when a user hits that button recording will start.

<button type="submit" class="btn btn-primary" data-toggle="tooltip" data-placement="top" onclick="record_session()" title="Start Recording">Record</button>

in my function below

function record_session(){
    //how can i trigger or initiate  ctrl+alt+r here??
}

Answer 1

If you use jQuery you can add keypress event:

$(document).keypress(function(e) {
    if (e.which === 114 && e.ctrlKey && e.altKey) {
        record_session();
    }
});

UPDATE :

var enable_keypress = false;
function record_session(){
    enable_keypress = true;
}
$(document).keypress(function(e) {
    if (enable_keypress) {
        if (e.which === 114 && e.ctrlKey && e.altKey) { // ctrl+alt+r

        }
    }
});

UPDATE 2

to fire keyboard event you can use this:

jQuery:

function keydown(ctrl, alt, shift, which, key) {
    var e = $.Event("keydown");
    e.ctrlKey = ctrl;
    e.altKey = alt;
    e.shiftKey = shift;
    if (typeof which === 'string') {
        key = which;
        which = key.toUpperCase().charCodeAt(0);
    }
    e.key = key;
    e.which = e.keyCode = which;
    return e;
}
function keypress(key) {
    var e = $.Event("keypress");
    e.key = key;
    e.which = e.keyCode = 0;
    return e;
}
function shortcut({
    ctrl = false,
    alt = false,
    shift = false,
    which,
    key
}) {
    var doc = $(document.documentElement || window);
    if (typeof which === 'string') {
        key = which;
        which = key.toUpperCase().charCodeAt(0);
    }
    doc.trigger(keydown(ctrl, alt, shift, which, key));
    doc.trigger(keypress(key));
}

you can use shortcut to trigger both keydown and keypress:

shortcut({ctrl: true, alt: true, which: 'r'});

in case you have listener that do different things (I have this in my tests for jQuery Terminal);

Native code:

 function shortcut({chr, ctrlKey = false, altKey = false}) {
     var lowerChr = chr.toLowerCase();
     var upperChr = chr.toUpperCase();
     var keydownCode = upperChr.charCodeAt(0);
     var e = new KeyboardEvent("keydown", {
         key: lowerChr,
         code: "Key" + upperChr,
         ctrlKey,
         altKey,
         keyCode: keydownCode,
         which: keydownCode
     });
     var keypressCode = lowerChr.charCodeAt(0);
     document.documentElement.dispatchEvent(e);
     var e = new KeyboardEvent("keypress", {
         key: lowerChr,
         ctrlKey,
         altKey,
         charCode: keypressCode,
         keyCode: keypressCode,
         which: keypressCode
     });
     document.documentElement.dispatchEvent(e);
 }