这次给大家带来js实现数字变化，js实现数字变化的注意事项有哪些，下面就是实战案例，一起来看一下。
$.fn.countTo = function (options) {
options = options || {};//当options未被初始化，即typeof options = 'undefined'时，执行后面部分即var options = {}来初始化一个对象
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);
}apply与call的简单用法，学习链接。
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