<SCRIPT LANGUAGE="JavaScript">
<!--var s = "aa+bb-cc*(dd+ee)/ff";
var r = s.match(/[^+\-*/()]+/g);
var mm = {};
if(r)
{
for(var i=0; i<r.length; i++)
{
if("undefined"==typeof(mm[r[i]]))
{
mm[r[i]] = r[i];
}
} var str = s;
for(var i in mm)
{
str = str.replace(new RegExp(i, "g"), prompt("请输入", 123));
}
alert(str);
var result = eval(str);
alert(result);
}//-->
</SCRIPT>
<!--var s = "aa+bb-cc*(dd+ee)/ff";
var r = s.match(/[^+\-*/()]+/g);
var mm = {};
if(r)
{
for(var i=0; i<r.length; i++)
{
if("undefined"==typeof(mm[r[i]]))
{
mm[r[i]] = r[i];
}
} var str = s;
for(var i in mm)
{
str = str.replace(new RegExp(i, "g"), prompt("请输入", 123));
}
alert(str);
var result = eval(str);
alert(result);
}//-->
</SCRIPT>
<!--var s = "aa+bb-cc*(dd+ee)/ff";
var r = s.match(/[^+\-*/()]+/g);
var mm = {};
if(r)
{
for(var i=0; i<r.length; i++)
{
if("undefined"==typeof(mm[r[i]]))
{
mm[r[i]] = r[i];
}
} var str = "方程式 = "+ s +"\n";
for(var i in mm)
{
mm[i] = prompt("请输入", 123);
s = s.replace(new RegExp(i, "g"), mm[i]);
str += i +"="+ mm[i] +"\n";
}
str += s +"\n";
str += "最后运行结果 = "+ eval(s)
alert(str);
}//-->
</SCRIPT>
s = 'aa+bb-cc*(dd+ee)/ff';
v = s.match(/\w+/g);for(i=0; i<v.length; i++) {
eval(v[i]+'='+i);
}
alert(eval(s));
</script>不完全符合你的要求,但就应该这样做