return $(this).each(function () {
// set options for current element
var settings = $.extend({},$.fn.countTo.defaults,{
from: $(this).data('from'),to: $(this).data('to'),speed: $(this).data('speed'),refreshInterval: $(this).data('refresh-interval'),decimals: $(this).data('decimals')
},options);

// how many times to update the value,and how much to increment the value on each update
//更新值多少次，每次更新值多快
var loops = Math.ceil(settings.speed / settings.refreshInterval),increment = (settings.to - settings.from) / loops;

// references & variables that will change with each update
//引用和变量每次更新将改变
var self = this,//返回html对象
$self = $(this),//返回返回一个jquery对象
loopCount = 0,value = settings.from,data = $self.data('countTo') || {};//获取jauery方法对象

$self.data('countTo',data);//赋值

// if an existing interval can be found,clear it first
//如果存在间隔，则清除它
if (data.interval) {
clearInterval(data.interval);
}
data.interval = setInterval(updateTimer,settings.refreshInterval);

// initialize the element with the starting value
//用开始的值初始化
render(value);

function updateTimer() {
value += increment;
loopCount++;

render(value);

if (typeof(settings.onUpdate) == 'function') {
settings.onUpdate.call(self,value);
}

if (loopCount >= loops) {
// remove the interval
$self.removeData('countTo');
clearInterval(data.interval);
value = settings.to;

if (typeof(settings.onComplete) == 'function') {
settings.onComplete.call(self,value);
}
}
}

function render(value) {
var formattedValue = settings.formatter.call(self,value,settings);
$self.html(formattedValue);
}
});
};

$.fn.countTo.defaults = {
from: 200,// the number the element should start at
to: 0,// the number the element should end at
speed: 1000,// how long it should take to count between the target numbers
refreshInterval: 1,// how often the element should be updated
decimals: 0,// the number of decimal places to show
formatter: formatter,// handler for formatting the value before rendering
onUpdate: null,// callback method for every time the element is updated
onComplete: null // callback method for when the element finishes updating
};

function formatter(value,settings) {
return value.toFixed(settings.decimals);
}

// custom formatting example
$('#count-number').data('countToOptions',{
formatter: function (value,options) {
return value.toFixed(options.decimals).replace(/\B(?=(?:\d{3})+(?!\d))/g,',');
}
});

// start all the timers
$('.timer').each(count);
function count(options) {
var $this = $(this);
options = $.extend({},options || {},$this.data('countToOptions') || {});
$this.countTo(options);
}