Question

function calcage(secs, num1, num2) {
  s = ((Math.floor(secs/num1))%num2).toString();
  if (LeadingZero && s.length < 2)
    s = "0" + s;
  return s;
}
function CountBack(secs)
{
  if (secs < 0) {
    document.getElementById("cntdwn").innerHTML = FinishMessage;
    return;
  }
  DisplayStr = DisplayFormat.replace(/%%D%%/g, calcage(secs,86400,100000));
  DisplayStr = DisplayStr.replace(/%%H%%/g, calcage(secs,3600,24));
  DisplayStr = DisplayStr.replace(/%%M%%/g, calcage(secs,60,60));
  DisplayStr = DisplayStr.replace(/%%S%%/g, calcage(secs,1,60));
  document.getElementById("cntdwn").innerHTML = DisplayStr;
  if (CountActive)
    setTimeout("CountBack(" + (secs+CountStepper) + ")", SetTimeOutPeriod);
}
function putspan() {
    document.write("<span id='cntdwn'></span>");
}
if (typeof(TargetDate)=="undefined")
  TargetDate = "12/31/2020 5:00 AM";
if (typeof(DisplayFormat)=="undefined")
  DisplayFormat = "%%D%% days, %%H%% hours, %%M%% minutes, %%S%% seconds";
if (typeof(CountActive)=="undefined")
  CountActive = true;
if (typeof(FinishMessage)=="undefined")
  FinishMessage = "Finished.";
if (typeof(CountStepper)!="number")
  CountStepper = -1;
if (typeof(LeadingZero)=="undefined")
  LeadingZero = true;

CountStepper = Math.ceil(CountStepper);
if (CountStepper == 0)
  CountActive = false;
var SetTimeOutPeriod = (Math.abs(CountStepper)-1)*1000 + 990;
putspan();
var dthen = new Date(TargetDate);
var dnow = new Date();
if(CountStepper>0)
  ddiff = new Date(dnow-dthen);
else
  ddiff = new Date(dthen-dnow);

gsecs = Math.floor(ddiff.valueOf()/1000);

CountBack(gsecs);

如果我把这段代码放在jQuery(function(){});里面，我得到：

ReferenceError: CountBack is not defined

为什么吗

Answer 1

如果在闭包内定义CountBack，则setTimeout将eval的javascript字符串将无法访问它。 setTimeout将eval()全局范围内的字符串参数。

永远不要将字符串传递给setTimeout！请改为执行此操作：

if (CountActive)
    setTimeout(function(){CountBack(secs+CountStepper);}, SetTimeOutPeriod);

Answer 2

将字符串传递给setTimeout会破坏范围（在全局范围而不是当前范围内进行评估）。传递一个函数。

功能未定义

2 个答案: