Check if adding an event listener is possible without adding one

Question

I want to add either a scroll event listener or a touchstart event listener. Initially I used the touch event to deactivate the scroll event listener as shown in the code below:

window.addEventListener('scroll', scrollStart, false);
window.addEventListener('touchstart', touchStart, false);

function scrollMenu() {
    // do something
}

function touchStart(e) {
    window.removeEventListener('scroll', scrollStart);
    // do something
}

But I realized that on some occasions, the scroll event is triggered as soon as the page loads. Therefore, I cannot use the aforementioned method. Is there another way to check if the browser supports a touch event listener without adding the event?

Paul Fleming · Accepted Answer · 2012-07-21 09:28:44Z

4

Does Modernizr solve your problem? See example here for the various ways to detect touch events and each one's browser compatibility:

http://modernizr.github.com/Modernizr/touch.html

answered Jul 21, 2012 at 9:28

Paul Fleming

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3 Comments

Matt Over a year ago

You should really include a summary of the detection methods mentioned in that link; what happens if the page goes down in the future? (see here)

Question Overflow Over a year ago

There are many methods, do I need to implement all or is ontouchstart in window the only relevant one?

Paul Fleming Over a year ago

You should probably do a browser check and use the method most appropriate to that browser. If you are only supporting a single browser, use the one that works for that browser.

Matt · Accepted Answer · 2012-07-21 09:28:57Z

3

You should be able to check whether the ontouchstart attribute exists in the window:

if ("ontouchstart" in window) {
    window.addEventListener('touchstart', touchStart, false);
} else {
    window.addEventListener('scroll', scrollStart, false);
}

... I can't confirm the x-browser-ness of this though.

answered Jul 21, 2012 at 9:28

Matt

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1 Comment

Question Overflow Over a year ago

Wow, this looks promising. Let me test it out.

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