How do I detect keypresses in Javascript?

With plain Javascript, the simplest is:

document.onkeypress = function (e) {
    e = e || window.event;
    // use e.keyCode
};

But with this, you can only bind one handler for the event.

In addition, you could use the following to be able to potentially bind multiple handlers to the same event:

addEvent(document, "keypress", function (e) {
    e = e || window.event;
    // use e.keyCode
});

function addEvent(element, eventName, callback) {
    if (element.addEventListener) {
        element.addEventListener(eventName, callback, false);
    } else if (element.attachEvent) {
        element.attachEvent("on" + eventName, callback);
    } else {
        element["on" + eventName] = callback;
    }
}

In either case, keyCode isn’t consistent across browsers, so there’s more to check for and figure out. Notice the e = e || window.event – that’s a normal problem with Internet Explorer, putting the event in window.event instead of passing it to the callback.

References:

• https://developer.mozilla.org/en-US/docs/DOM/Mozilla_event_reference/keypress
• https://developer.mozilla.org/en-US/docs/DOM/EventTarget.addEventListener

With jQuery:

$(document).on("keypress", function (e) {
    // use e.which
});

Reference:

• http://api.jquery.com/on/

Other than jQuery being a “large” library, jQuery really helps with inconsistencies between browsers, especially with window events…and that can’t be denied. Hopefully it’s obvious that the jQuery code I provided for your example is much more elegant and shorter, yet accomplishes what you want in a consistent way. You should be able to trust that e (the event) and e.which (the key code, for knowing which key was pressed) are accurate. In plain Javascript, it’s a little harder to know unless you do everything that the jQuery library internally does.

Note there is a keydown event, that is different than keypress. You can learn more about them here: onKeyPress Vs. onKeyUp and onKeyDown

As for suggesting what to use, I would definitely suggest using jQuery if you’re up for learning the framework. At the same time, I would say that you should learn Javascript’s syntax, methods, features, and how to interact with the DOM. Once you understand how it works and what’s happening, you should be more comfortable working with jQuery. To me, jQuery makes things more consistent and is more concise. In the end, it’s Javascript, and wraps the language.

Another example of jQuery being very useful is with AJAX. Browsers are inconsistent with how AJAX requests are handled, so jQuery abstracts that so you don’t have to worry.

Here’s something that might help decide:

• http://www.jscripters.com/jquery-disadvantages-and-advantages/