字符串大小比较

var a = "1234",b = "2345";
console.log(b>a);
result: true

var a = "1234",b = "2345";
console.log(a>b);
result: false

var starttime = byId('startTime_hour').value+""+byId('starTime_minute').value;
var endtime = byId('endTime_hour').value+""+byId('endTime_minute').value;
if(starttime >= endtime ){
byId("lesson_endTime_error").innerHTML = "* 结束时间不能早于开始时间";
byId("lesson_endTime_error").style.display = "inline-block";
return;
}