“一些”发布的代码的改进版本

/* Compare the current date against another date.
 *
 * @param b  {Date} the other date
 * @returns   -1 : if this < b
 *             0 : if this === b
 *             1 : if this > b
 *            NaN : if a or b is an illegal date
*/ 
Date.prototype.compare = function(b) {
  if (b.constructor !== Date) {
    throw "invalid_date";
  }

 return (isFinite(this.valueOf()) && isFinite(b.valueOf()) ? 
          (this>b)-(this<b) : NaN 
        );
};

用法：

  var a = new Date(2011, 1-1, 1);
  var b = new Date(2011, 1-1, 1);
  var c = new Date(2011, 1-1, 31);
  var d = new Date(2011, 1-1, 31);

  assertEquals( 0, a.compare(b));
  assertEquals( 0, b.compare(a));
  assertEquals(-1, a.compare(c));
  assertEquals( 1, c.compare(a));

另一种比较两个日期的方法是通过toISOString（）方法。这在与保存在字符串中的固定日期进行比较时特别有用，因为可以避免创建短时间对象。借助ISO 8601格式，您可以按字典方式比较这些字符串（至少在使用相同时区时）。

我不一定说它比使用时间对象或时间戳更好；只是将此作为另一种选择。这可能会失败，但我还没有发现：）

function datesEqual(a, b)
{
   return (!(a>b || b>a))
}

var curDate=new Date();
var startDate=document.forms[0].m_strStartDate;

var endDate=document.forms[0].m_strEndDate;
var startDateVal=startDate.value.split('-');
var endDateVal=endDate.value.split('-');
var firstDate=new Date();
firstDate.setFullYear(startDateVal[2], (startDateVal[1] - 1), startDateVal[0]);

var secondDate=new Date();
secondDate.setFullYear(endDateVal[2], (endDateVal[1] - 1), endDateVal[0]);
if(firstDate > curDate) {
    alert("Start date cannot be greater than current date!");
    return false;
}
if (firstDate > secondDate) {
    alert("Start date cannot be greater!");
    return false;
}

“一些”发布的代码的改进版本

/* Compare the current date against another date.
 *
 * @param b  {Date} the other date
 * @returns   -1 : if this < b
 *             0 : if this === b
 *             1 : if this > b
 *            NaN : if a or b is an illegal date
*/ 
Date.prototype.compare = function(b) {
  if (b.constructor !== Date) {
    throw "invalid_date";
  }

 return (isFinite(this.valueOf()) && isFinite(b.valueOf()) ? 
          (this>b)-(this<b) : NaN 
        );
};

用法：

  var a = new Date(2011, 1-1, 1);
  var b = new Date(2011, 1-1, 1);
  var c = new Date(2011, 1-1, 31);
  var d = new Date(2011, 1-1, 31);

  assertEquals( 0, a.compare(b));
  assertEquals( 0, b.compare(a));
  assertEquals(-1, a.compare(c));
  assertEquals( 1, c.compare(a));

function compare_date(date1, date2){
const x = new Date(date1)
const y = new Date(date2)
function checkyear(x, y){
    if(x.getFullYear()>y.getFullYear()){
        return "Date1 > Date2"
    }
    else if(x.getFullYear()<y.getFullYear()){
        return "Date2 > Date1"
    }
    else{
        return checkmonth(x, y)
    }
}
function checkmonth(x, y){
    if(x.getMonth()>y.getFullYear()){
        return "Date1 > Date2"
    }
    else if(x.getMonth()<y.getMonth){
        return "Date2 > Date1"
    }
    else {
        return checkDate(x, y)
    }
}
function checkDate(x, y){
    if(x.getDate()>y.getFullYear()){
        return "Date1 > Date2"
    }
    else if(x.getDate()<y.getDate()){
        return "Date2 > Date1"
    }
    else {
        return checkhour(x,y)
    }
}
function checkhour(x, y){
    if(x.getHours()>y.getHours()){
        return "Date1 > Date2"
    }
    else if(x.getHours()<y.getHours()){
        return "Date2 > Date1"
    }
    else {
        return checkhmin(x,y)
    }
}
function checkhmin(x,y){
    if(x.getMinutes()>y.getMinutes()){
        return "Date1 > Date2"
    }
    else if(x.getMinutes()<y.getMinutes()){
        return "Date2 > Date1"
    }
    else {
        return "Date1 = Date2"
    }
}
return checkyear(x, y)