Joho the Blog » keypress

July 22, 2012

Capturing control keys in Chrome et al.

Hallelujah! For years — literally years — I’ve been limping along with a blender full of spaghetti to do something that should be really simple: capture control key combos (like CTRL-S or CTRL-I) via Javascript in all the major browsers. I finally found some simple code that seems to work beautifully.

The problem is that the browsers don’t agree about what’s going on when a user presses a control key and another key simultaneously, which is, after all, the usual thing people do with the control key. Some of the browsers think that it’s two events, so you have to record the control keypress, remember it, and treat the next keypress differently. Other browsers think of it as a single keypress that you can just process as a if CTRL-S were a unique key. Then, depending, you may or may not have to nullify the S press. The way I was doing it (cribbed from multiple sources, of course) involved first checking on which browser the Javascript was running in, and then process keystrokes, looking for an initial control press. Pain in the butt, and it was fragile.

I am certain that this is not a problem for actual developers. For example, jquery handles keystrokes, although I had trouble getting it to work (becaues, if it’s not clear, I am a ham-fisted hobbyist who mainly just copies in other people’s code. Thank you, other people!)

Today I had a a few minutes, so I went back to Google and found some simple code from Ganesh. Thank you!

Here’s what you do:

First, include jQuery. Place the following into your Javascript the following block. Put it toward the top, and don’t put inside a function. You want it to run whenever your Javascript loads. (Well, you could put it into an initialization function if you want.)

$.ctrl = function(key, callback, args) {
    $(document).keydown(function(e) {
        if(!args) args=[]; // IE barks when args is null 
        if(e.keyCode == key.charCodeAt(0) && e.ctrlKey) {
            callback.apply(this, args);
            return false;

After that, you can bind a control combo, such as Control-S, to the function you want (e.g., “SaveMe()”) this way:

$.ctrl('S', function() {

By the way, Ganesh thanks an anonymous commenter for improving the code. God bless the iterative Web!

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