对这段代码不明白，

2012-02-02

对这段代码不明白，请指教。HTML codeSCRIPTvar Lastyearfunction selYear(obj,Cyear){var len8 //select

对这段代码不明白，请指教。

HTML code

<SCRIPT>var Lastyearfunction selYear(obj,Cyear){var len=8 //select长度var selObj=document.getElementById(obj)var selIndex=parseInt(len/2)-1var newOptvar LY=Cyear-Lastyearfor (i=0;i<len;i++){   if (selObj.options.length!=len){     newOpt=document.createElement("OPTION")     newOpt.text=Cyear-selIndex+i     newOpt.value=Cyear-selIndex+i     selObj.options.add(newOpt,i)      if (selIndex==i) {Lastyear=newOpt.value}           }    else    {  //不明白，这段代码什么时候执行到，     selObj.options[i].text=parseInt(selObj.options[i].text)+LY     selObj.options[i].value=parseInt(selObj.options[i].value)+LY     if (selIndex==i) {Lastyear=selObj.options[i].value}               } }  selObj.selectedIndex=selIndex}</SCRIPT><SELECT id=yearSelect onChange="selYear('yearSelect',this.value)" size=1 name=yearSelect></SELECT><SCRIPT>selYear('yearSelect',new Date().getFullYear()) //初试化select</SCRIPT>

[解决办法]
初试化完里面有8个option
这时候selObj.options.length 为8 执行else

[解决办法]

JScript code

<html> <head> <title> SCROLL </title> <SCRIPT>var Lastyearfunction selYear(obj,Cyear){var len=8 //select长度var selObj=document.getElementById(obj)var selIndex=parseInt(len/2)-1var newOptvar LY=Cyear-Lastyearfor (i=0;i<len;i++){   if (selObj.options.length!=len){     newOpt=document.createElement("OPTION")     newOpt.text=Cyear-selIndex+i     newOpt.value=Cyear-selIndex+i     selObj.options.add(newOpt,i)      if (selIndex==i) {Lastyear=newOpt.value}           }    else    {  //不明白，这段代码什么时候执行到，     selObj.options[i].text=parseInt(selObj.options[i].text)+LY     selObj.options[i].value=parseInt(selObj.options[i].value)+LY     if (selIndex==i) {Lastyear=selObj.options[i].value}               } }  selObj.selectedIndex=selIndex}</SCRIPT><body> <SELECT id=yearSelect onChange="selYear('yearSelect',this.value)" size=1 name=yearSelect></SELECT></body> <SCRIPT>selYear('yearSelect',new Date().getFullYear()) //初试化select</SCRIPT><SELECT id=yearSelect2 onChange="selYear('yearSelect2',this.value)" size=1 name=yearSelect2><option value="1999">1999</option><option value="1999">1999</option><option value="1999">1999</option><option value="1999">1999</option><option value="1999">1999</option><option value="1999">1999</option><option value="1999">1999</option><option value="1999">1999</option><option value="1999">1999</option></SELECT></html>
[解决办法]
初始化时不执行，当初始化完成，以后在选中某一选项调用onChange="selYear('yearSelect',this.value)"方法时执行else

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对这段代码不明白，