日期比较：

var str1  = document.getElementById("Fromdate").value;
var str2  = document.getElementById("Todate").value;
var dt1   = parseInt(str1.substring(0,2),10); 
var mon1  = parseInt(str1.substring(3,5),10);
var yr1   = parseInt(str1.substring(6,10),10); 
var dt2   = parseInt(str2.substring(0,2),10); 
var mon2  = parseInt(str2.substring(3,5),10); 
var yr2   = parseInt(str2.substring(6,10),10); 
var date1 = new Date(yr1, mon1, dt1); 
var date2 = new Date(yr2, mon2, dt2); 

if(date2 < date1)
{
   alert("To date cannot be greater than from date");
   return false; 
} 
else 
{ 
   alert("Submitting ...");
   document.form1.submit(); 
} 

var date_today=new Date();
var formated_date = formatDate(date_today);//Calling formatDate Function

var input_date="2015/04/22 11:12 AM";

var currentDateTime = new Date(Date.parse(formated_date));
var inputDateTime   = new Date(Date.parse(input_date));

if (inputDateTime <= currentDateTime){
    //Do something...
}

function formatDate(date) {
    var hours = date.getHours();
    var minutes = date.getMinutes();
    var ampm = hours >= 12 ? 'PM' : 'AM';

    hours = hours % 12;
    hours = hours ? hours : 12; // the hour '0' should be '12'
    hours   = hours < 10 ? '0'+hours : hours ;

    minutes = minutes < 10 ? '0'+minutes : minutes;

    var strTime = hours+":"+minutes+ ' ' + ampm;
    return  date.getFullYear()+ "/" + ((date.getMonth()+1) < 10 ? "0"+(date.getMonth()+1) :
    (date.getMonth()+1) ) + "/" + (date.getDate() < 10 ? "0"+date.getDate() :
    date.getDate()) + " " + strTime;
}

var date = new Date(); // will give you todays date.

// following calls, will let you set new dates.
setDate()   
setFullYear()   
setHours()  
setMilliseconds()   
setMinutes()    
setMonth()  
setSeconds()    
setTime()

var yesterday = new Date();
yesterday.setDate(...date info here);

if(date>yesterday)  // will compare dates

如果两个日期的格式都是“YYYY-MM-DD”，则可以跳过Date对象，直接比较字符串。

这是因为JS中字符串的比较方式

let date1 = '2022-12-13';
let date2 = '2022-02-13';

console.log(`${date1} > ${date2}`, date1 > date2);
console.log(`${date1} < ${date2}`, date1 < date2);
console.log(`${date1} == ${date2}`, date1 == date2);

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

试试这个而比较日期应为iso格式“yyyy-MM-dd”如果要仅比较日期，请使用此datehelper

<a href="https://plnkr.co/edit/9N8ZcC?p=preview"> Live Demo</a>