javascript - new Date() returns undefined - Stack Overflow

I have this code:

function submit(){
//Some stuff here...

clicked= false

//Some stuff here...

function start() {
    var starttime;
    if(clicked===false)
    {
        document.getElementById("start").innerHTML = "Submit";
        starttime = new Date();
        document.getElementById("title").innerHTML = "<b>...</b>";
        clicked=true;
    } else {
        var endtime = new Date();
        var timediff = endtime - starttime;
        alert(typeof endtime + typeof starttime + typeof timediff + timediff + endtime + starttime);
        submit();
    }
}

timediff always returns NaN. When I use typeof, starttime is undefined, endtime is an object and timediff is a number. Why? Is there a solution? Thanks

I have this code:

function submit(){
//Some stuff here...

clicked= false

//Some stuff here...

function start() {
    var starttime;
    if(clicked===false)
    {
        document.getElementById("start").innerHTML = "Submit";
        starttime = new Date();
        document.getElementById("title").innerHTML = "<b>...</b>";
        clicked=true;
    } else {
        var endtime = new Date();
        var timediff = endtime - starttime;
        alert(typeof endtime + typeof starttime + typeof timediff + timediff + endtime + starttime);
        submit();
    }
}

timediff always returns NaN. When I use typeof, starttime is undefined, endtime is an object and timediff is a number. Why? Is there a solution? Thanks

• javascript
• undefined
• nan

Share Improve this question Follow asked Apr 10, 2017 at 8:26 Bill RBill R 2311 silver badge55 bronze badges 2

• Define var starttime; outside the function – Satpal Commented Apr 10, 2017 at 8:28
• It's defined within function scope; the second time start is called it has no value. Move the declaration to the containing scope, similar to clicked – pinkfloydx33 Commented Apr 10, 2017 at 8:29

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5 Answers 5

Sorted by: Reset to default 1

You need to make starttime global in order for this to work:

clicked= false;
var starttime;

//Some stuff here...

function start() {

    if(clicked === false) {
        document.getElementById("start").innerHTML = "Submit";
        starttime = new Date();
        document.getElementById("title").innerHTML = "<b>...</b>";
        clicked=true;
    } else {
        var endtime = new Date();
        var timediff = endtime - starttime;
        alert(typeof endtime + typeof starttime + typeof timediff + timediff + endtime + starttime);
        submit();
    }
}

Use getTime function on the Date object to get the difference

function submit(){
 //Some stuff here...

clicked= false

 //Some stuff here...

function start() {
  var starttime;
  if(clicked===false)
  {
    document.getElementById("start").innerHTML = "Submit";
    starttime = new Date();
    document.getElementById("title").innerHTML = "<b>...</b>";
    clicked=true;
   } else {
    var endtime = new Date();
    var timediff = endtime.getTime() - starttime.getTime();

    submit();
}
 }

1. Need to call start function
2. clicked variable is false thus executing if(clicked===false) block

3. Making clicked to true will not instantiate starttime

   function submit(){
       var clicked= true;
   
   function start() {
       var starttime = new Date();
       if(!clicked)
       {
           alert("When clicked is : "+clicked);
           alert(starttime);
           clicked=true;
       } else {
           alert("When clicked is : "+clicked)
           var endtime = new Date();
           var timediff = endtime - starttime;
           /*
           alert(typeof starttime);
           alert(typeof endtime);
           alert(typeof timediff);
           */
           alert("starttime "+starttime);
           alert("endtime "+endtime);
           alert("timediff "+timediff);
       }
     }
      start();
   }
   submit();
   

Hope this solution will help you...

For this please declare both variable outside of the function

clicked= false 

var starttime;

and it will look like :

 clicked= false;

 var starttime;

function start()
{

//your code

}

Rest of the code is fine.

you are having endtime as an object because new Date() returns one. You can use new Date().getTime() to return the number of milliseconds between midnight of January 1, 1970 and the specified/current date.

startTime is undefined because you didn't initialize it so if the else block runs, its value will be undefined. So I hope this solves your problem.

function submit(){
//Some stuff here...

var starttime = new Date().getTime();
var clicked = false

//Some stuff here...

function start() {

    if(clicked===false)
    {
        document.getElementById("start").innerHTML = "Submit";
        //starttime = new Date();
        document.getElementById("title").innerHTML = "<b>...</b>";
        clicked=true;
    } else {
        var endtime = new Date().getTime();
        var timediff = endtime - starttime;
        alert(typeof endtime + typeof starttime + typeof timediff + timediff + endtime + starttime);
        submit();
    }
}

Yon can always convert startTime and endTime into date strings by passing them as arguments to new Date() and using any of the conversion methods.

new Date(1491813677908).toString();
new Date(1491813677908).toLocaleString();

Take care.