javascript: how to loop through date object

Question

I'm not sure how to ask this, but is there a way to get the current local full year and then create a loop to get the last 18 years and print them to the screen?

Here is what I've tried...

function allYears(){
  var d = new Date();
  var y = d.getFullYear();
  var years = '';
  for(var i=0; i>18; i++){
    years += '<option value="'+y+'">'+y+'</option>';
    y = y-1;
  }
return(years);
}

The body of your loop is never executed since i = 0 and 0 > 18 is false. — Felix Kling
– Felix Kling, Commented Jul 24, 2012 at 20:26
+1 Felix Kling, your comment was very helpful! I set up some alerts but the for loop would never execute and I couldn't figure out why. Thank you! — Juan Gonzales
– Juan Gonzales, Commented Jul 24, 2012 at 21:28

Mitya · Accepted Answer · 2012-07-24 20:56:04Z

2

You're close, but two problems:

1) d.getFullYear should be d.getFullYear(), otherwise you're not getting the year, merely referencing the method

2) > 18 should be < 18

edited Jul 24, 2012 at 20:56

answered Jul 24, 2012 at 20:22

Mitya

34.8k15 gold badges70 silver badges126 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

RestingRobot · Accepted Answer · 2012-07-24 21:26:15Z

1

Fiddle with working example: http://jsfiddle.net/aMFpw/6/

You were very close with your original implementaion.

Javascript here:

  function getYears(num){
    var d  = new Date();
    var y = parseInt(d.getFullYear());

    var years = "";

    //need to add one to our number based on our loop index.
    num++;

    for(var i=0; i<num; i++){
        years += '<option value="' + y + '">' + y + '</option>';
        y--;    
    }

    return years;
 }

edited Jul 24, 2012 at 21:26

answered Jul 24, 2012 at 21:19

RestingRobot

2,9881 gold badge25 silver badges36 bronze badges

Comments

bokonic · Accepted Answer · 2012-07-24 22:13:56Z

0

As a function:

function printYearsBefore(date,num) {
   var yr = parseInt(date.getFullYear()), i =0;
   while(++i <= num){
     document.write((yr-i));
   }
}

printYearsBefore(new Date(),18);

edited Jul 24, 2012 at 22:13

answered Jul 24, 2012 at 20:22

bokonic

1,77110 silver badges12 bronze badges

1 Comment

RestingRobot Over a year ago

This only produces 17 previous years. You should change the while condition to ++i <= num.

David Thomas · Accepted Answer · 2012-07-24 20:29:10Z

0

I'd suggest performing math on the variable that refers to the year, as you increment (or decrement) through the for loop, simply add, or remove, the incrementing variable (i in this case) to, or from, the variable holding the year:

function addYears(el, num) {
    if (!el) {
        return false;
    }
    else {
        for (var i=0; i < num; i++) {
            var opt = document.createElement('option'),
                year = new Date().getFullYear() - i;
            opt.value = year;
            opt.textContent = year;
            el.appendChild(opt);
        }
    }
}

addYears(document.getElementById('years'), 18);

JS Fiddle proof of concept.

In your code excerpt, I'd suggest amending things to:

function allYears(){
  var d = new Date();
  var y = d.getFullYear();
  var years = '';
  for(var i=0; i<18; i++){
    years += '<option value="'+ (y - i) +'">'+ (y - i) +'</option>';
  }
return(years);
}

Which, as the loop progresses, should return option elements with year values progressively earlier than the year held in y.

Also, the middle condition in the for loop is the evaluation that has to be true for the loop to continue (when it stops being true is when the loop exits), so it should be i < 18 (since i starts equal to 0).

edited Jul 24, 2012 at 20:29

answered Jul 24, 2012 at 20:19

David Thomas

254k53 gold badges382 silver badges421 bronze badges

1 Comment

RestingRobot Over a year ago

This code only produces the last 17 years, not 18 like the answer specifies.

Collectives™ on Stack Overflow

javascript: how to loop through date object

4 Answers 4

Comments

Comments

1 Comment

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

4 Answers 4

Comments

Comments

1 Comment

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related