How to calculate date difference in JavaScript?

Question

I want to calculate date difference in days, hours, minutes, seconds, milliseconds, nanoseconds. How can I do it?

Answer 1

function daysInMonth (month, year) {
    return new Date(year, month, 0).getDate();
}
function getduration(){

let A= document.getElementById("date1_id").value
let B= document.getElementById("date2_id").value

let C=Number(A.substring(3,5))
let D=Number(B.substring(3,5))
let dif=D-C
let arr=[];
let sum=0;
for (let i=0;i0||Number(B.substring(0,2)) - Number(A.substring(0,2))<0){
days=Number(B.substring(0,2)) - Number(A.substring(0,2)) + sum_alter
}

if ((Number(B.substring(3,5)) == Number(A.substring(3,5)))){
console.log(Number(B.substring(0,2)) - Number(A.substring(0,2)) + sum_alter)
}

time_1=[]; time_2=[]; let hour=[];
 time_1=document.getElementById("time1_id").value
 time_2=document.getElementById("time2_id").value
  if (time_1.substring(0,2)=="12"){
     time_1="00:00:00 PM"
  }
if (time_1.substring(9,11)==time_2.substring(9,11)){
hour=Math.abs(Number(time_2.substring(0,2)) - Number(time_1.substring(0,2)))
}
if (time_1.substring(9,11)!=time_2.substring(9,11)){
hour=Math.abs(Number(time_2.substring(0,2)) - Number(time_1.substring(0,2)))+12
}
let min=Math.abs(Number(time_1.substring(3,5))-Number(time_2.substring(3,5)))
document.getElementById("duration_id").value=days +" days "+ hour+"  hour " + min+"  min " 
}

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