usage of for loop in javascript

Question

I need to write program that will take first input as 'i' and this loop need to go until first input is less or equal to second input. what I had written but seems not working:

function provjeri() {

    var i  = document.getElementById('prvi').value;
    var b = document.getElementById('drugi').value;
    var c = "";

    for (; parseInt(i) <= parseInt(b)  ; i+=2) {
        c+=i ;
    }

    document.getElementById('rez').innerHTML = parseInt(c);
}

e.g. first input is 3 secound input is 7, output is 3 plus 5 plus 7 equal 15 — Hotshot
– Hotshot, Commented Apr 13, 2016 at 15:49
I don't think you can use a for loop like that. A for loop has a clear syntax which contains the declaration of the index to loop over. You should use a while loop. Additionally you are cancating strings rather than doing mathematics. Your result will be "357" not 15 because you define c as a string and then add a string to it. — Danmoreng
– Danmoreng, Commented Apr 13, 2016 at 15:52
You can use for loops like that, just don't see it used too often. — IrkenInvader
– IrkenInvader, Commented Apr 13, 2016 at 15:58
It is often viewed as more correct to use loops like that because it allows you to keep all your variable declarations in one place, usually the start of the function. — Fergal Andrews
– Fergal Andrews, Commented Apr 13, 2016 at 16:10
One possible issue is that you are using parseInt in your loop declaration for the first 'i' but not the second or the 'i' in the loop body. These will be treated as strings, as will c as it is declared using c="". There could be other problems also. — Fergal Andrews
– Fergal Andrews, Commented Apr 13, 2016 at 16:16

Munawir · Accepted Answer · 2016-04-13 16:08:59Z

1

parseInt() when getting the value. Also use c=0, c="" is considered as a string and new values are concatinated to c

function provjeri() {
  var i = parseInt(document.getElementById('prvi').value);
  var b = parseInt(document.getElementById('drugi').value);
  var c = 0;
  
  for (; i <= b  ; i+=2) {
    c+=i ;
  }
  document.getElementById('rez').innerHTML = parseInt(c);	
}

<input id='prvi' />
<input id='drugi' />
<button onclick='provjeri()'>Calc</button><br>
<span id='rez'></span>

answered Apr 13, 2016 at 16:08

Munawir

3,3569 gold badges36 silver badges51 bronze badges

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

Comments

gabesoft · Accepted Answer · 2016-04-13 15:55:52Z

0

You can do it like this

var k = 0;
var ival = parseInt(i);
var bval = parseInt(v);

for (k = ival; k <= bval; k += 2) {
   c += k;
}

answered Apr 13, 2016 at 15:55

gabesoft

1,2289 silver badges6 bronze badges

Comments

isvforall · Accepted Answer · 2016-04-13 16:00:23Z

0

I guess, you are looking for this:

function provjeri() {
    var i = document.getElementById('prvi').value;
    var b = document.getElementById('drugi').value;
    var c = 0; // needs to be a number
    i = parseInt(i, 10);
    b = parseInt(b, 10);

    for (; i <= b; i += 2) {
        c += i;
    }
    document.getElementById('rez').innerHTML = c;
}

<input id='prvi'></input>
<input id='drugi'></input>
<button onclick='provjeri()'>call function</button><br>
<span id='rez'></span>

edited Apr 13, 2016 at 16:00

answered Apr 13, 2016 at 15:56

isvforall

8,9166 gold badges39 silver badges52 bronze badges

2 Comments

Danmoreng Over a year ago

You also defined c as a string which makes it concat rather than add up. Edit: better now.

isvforall Over a year ago

@Hotshot 0246 is it desired output, or it's error? just tried, snippet working fine

Danmoreng · Accepted Answer · 2016-04-13 16:02:15Z

0

This is how it should look like:

function provjeri() {
    var i  = parseInt(document.getElementById('prvi').value);
    var b = parseInt(document.getElementById('drugi').value);
    var c = 0;
    while(i <= b){
       c += i;
       i += 2;
    }
    document.getElementById('rez').innerHTML = c;
}

edited Apr 13, 2016 at 16:02

answered Apr 13, 2016 at 15:56

Danmoreng

2,3671 gold badge20 silver badges32 bronze badges

Collectives™ on Stack Overflow

usage of for loop in javascript

4 Answers 4

Comments

Comments

2 Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

4 Answers 4

Comments

Comments

2 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related