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index.js
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index.js
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/**
* Module dependencies.
*/
var Tween = require('tween');
var raf = require('raf');
/**
* Expose `scrollTo`.
*/
module.exports = scrollTo;
/**
* Scroll to `(x, y)`.
*
* @param {Number} x
* @param {Number} y
* @api public
*/
function scrollTo(x, y, options) {
options = options || {};
// start position
var start = scroll(options.box);
if (options.box && options.box.scrollTop) {
y = y + options.box.scrollTop;
}
// setup tween
var tween = Tween(start)
.ease(options.ease || 'out-circ')
.to({ top: y, left: x })
.duration(options.duration || 1000);
// scroll
tween.update(function(o){
if (options.box) options.box.scrollTop = o.top;
else window.scrollTo(o.left | 0, o.top | 0);
});
// handle end
tween.on('end', function(){
animate = function(){};
});
// animate
function animate() {
raf(animate);
tween.update();
}
animate();
return tween;
}
/**
* Return scroll position.
*
* @return {Object}
* @api private
*/
function scroll(box) {
var y = (box && box.scrollTop) || this.pageYOffset || document.documentElement.scrollTop;
var x = (box && box.scrollLeft) || this.pageXOffset || document.documentElement.scrollLeft;
return { top: y, left: x };
}