Cross browser JavaScript (not jQuery…) scroll to top animation

Question

I\'m looking for a simple, cross-browser \"scroll to top\" animation I can apply to a link. I don\'t want to require a JS library such as jQuery/Moo, etc.

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Answer 1

I modified the code of @TimWolla to add more options and a some movement functions. Also, added support to crossbrowser with document.body.scrollTop and document.documentElement.scrollTop

// scroll to top
scrollTo(0, 1000);

// Element to move, time in ms to animate
function scrollTo(element, duration) {
    var e = document.documentElement;
    if(e.scrollTop===0){
        var t = e.scrollTop;
        ++e.scrollTop;
        e = t+1===e.scrollTop--?e:document.body;
    }
    scrollToC(e, e.scrollTop, element, duration);
}

// Element to move, element or px from, element or px to, time in ms to animate
function scrollToC(element, from, to, duration) {
    if (duration <= 0) return;
    if(typeof from === "object")from=from.offsetTop;
    if(typeof to === "object")to=to.offsetTop;

    scrollToX(element, from, to, 0, 1/duration, 20, easeOutCuaic);
}

function scrollToX(element, xFrom, xTo, t01, speed, step, motion) {
    if (t01 < 0 || t01 > 1 || speed<= 0) {
        element.scrollTop = xTo;
        return;
    }
    element.scrollTop = xFrom - (xFrom - xTo) * motion(t01);
    t01 += speed * step;

    setTimeout(function() {
        scrollToX(element, xFrom, xTo, t01, speed, step, motion);
    }, step);
}
function easeOutCuaic(t){
    t--;
    return t*t*t+1;
}

http://jsfiddle.net/forestrf/tPQSv/

Minified version: http://jsfiddle.net/forestrf/tPQSv/139/

// c = element to scroll to or top position in pixels
// e = duration of the scroll in ms, time scrolling
// d = (optative) ease function. Default easeOutCuaic
function scrollTo(c,e,d){d||(d=easeOutCuaic);var a=document.documentElement;if(0===a.scrollTop){var b=a.scrollTop;++a.scrollTop;a=b+1===a.scrollTop--?a:document.body}b=a.scrollTop;0>=e||("object"===typeof b&&(b=b.offsetTop),"object"===typeof c&&(c=c.offsetTop),function(a,b,c,f,d,e,h){function g(){0>f||1=d?a.scrollTop=c:(a.scrollTop=b-(b-c)*h(f),f+=d*e,setTimeout(g,e))}g()}(a,b,c,0,1/e,20,d))};
function easeOutCuaic(t){
    t--;
    return t*t*t+1;
}