js代码，变量理解的问题。

[qq_39402915]

date，timeidx两个变量在js文档中并没有定义，如果function是回调函数那么date，timeidx该如何理解
window.onload = function () {
var hhi = $(window).height() - 210;
var wwi = document.getElementById('header').offsetWidth - 133;
$("#map_div").css("height", hhi + "px");
$("#map_div").css("width", wwi + "px");

require(["view/leaflet", "view/dtimePicker", "util/player", "view/Initial"], function (leaflet, dtimePicker, player, init) {
var _initial = new init.Initial();
productLayer = _initial.InitleafletMap(leaflet);
dateTimeWidget = _initial.InitDateTimePicker(dtimePicker, BindNewDataTimesLine, function (dateList) {
playWidget = _initial.InitPlayWidget(player, dateList);
}, setPickerDateTime);
});
windCanvas = new windlayer();
GISView.init();
var b= function(err){
console.info(err);
}
productLayer.getUrl = function (date, timeidx) {
//console.info(date);
$('#map_time').text('预报时间：' + date.format('yyyy年MM月dd日 HH:mm'));
GISView.timeIndex = timeidx;
GISView.LoadWindPath(date);
GISView.LoadECPath(date);
return "";
}
}