function tap(el,fn){var startPoint = {};
el.addEventListener('touchstart', function(e) {
startPoint = {x: e.changedTouches[0].pageX,
y: e.changedTouches[0].pageY
};
});
el.addEventListener('touchend', function(e) {
var nowPoint = {x: e.changedTouches[0].pageX,
y: e.changedTouches[0].pageY
};
if(Math.abs(nowPoint.x - startPoint.x) < 5
&&Math.abs(nowPoint.y - startPoint.y) < 5) {fn&&fn.call(el,e)
}
});
}