Cross Browser Scroll to Top Animation (JavaScript)

Minggu, 23 Juni 2013

/*! http://stackoverflow.com/questions/8917921/cross-browser-javascript-not-jquery-scroll-to-top-animation */
function scrollTo(element, to, duration) {

    // http://robertpenner.com/easing/
    // t = current time, b = start value, c = change in value, d = duration
    Math.easeInOutQuad = function(t, b, c, d) {
        t /= d / 2;
        if (t < 1) return c / 2 * t * t + b;
        t--;
        return -c / 2 * (t * (t - 2) - 1) + b;
    };

    var start = element.scrollTop,
        change = to - start,
        currentTime = 0,
        increment = 20,
        animateScroll = function() {
            currentTime += increment;
            var val = Math.easeInOutQuad(currentTime, start, change, duration);
            element.scrollTop = val;
            if (currentTime < duration) {
                setTimeout(animateScroll, increment);
            }
        };

    animateScroll();

}

Penggunaan

element digunakan untuk mewakili elemen yang ingin diberi efek animasi, to mewakili jarak arah gulungan ke atas, duration mewakili durasi animasi:

<button onclick="scrollTo(document.body, 0, 1000);">Scroll to Top</button>

Lihat Demo

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