For loop with two counters, and confusing if-else statements.(JavaScript)

Question

<!doctype html>
<html>
  <head>
    <script>
      function do_something() {
        var theBody = document.getElementsByTagName("body")[0];
        var theImg = document.createElement("img");
        theImg.src = "cat.png";
        theBody.appendChild(theImg.cloneNode(true));
        var count = 0;
        for (var i = 0; i < 10; i++, count++) {
            if (i == 5) continue;
            if (count == 3) {
                count = 0;
                theBody.removeChild(theBody.lastChild);
            } else {
                theBody.appendChild(theImg.cloneNode(true));
            }
            if (i > 7) break;
        }
      }
    </script>
  </head>
  <body onload="do_something()"></body>
</html>

I am supposed to tell how many images would a modern browser display.

I have two major doubts here:

When i=4, what is the value of count? I think it would be 0, but don't why I am confused about it.
As the code tells, when count = 0, an image will be removed from the body. Does the code append an image, and then remove an image? Or, does it simply remove one image? This is the part that is confusing because nothing is said about what happens when i=3.

According to the given answer, 6 images are added in the loop, and 2 are removed. So, a total number of 5 images are displayed.

1. Yes, it will be 4. 2. It removes the third and sixth image, making it totally 5 images, as the numbers are 0 starting. 0 - 6 is seven images, out of which two are removed leaving five images. — Praveen Kumar Purushothaman
– Praveen Kumar Purushothaman, Commented Oct 1, 2016 at 12:35
As a note: Beside many others this is a good situation to use the javascript debugger build into all modern browsers, and step through the code instruction by instruction. Then you exactly see what happens. — t.niese
– t.niese, Commented Oct 1, 2016 at 12:39
@PraveenKumar I didn't get it, count = 4 ? Doesn't it get reset to 0, once it reaches 3? Also, wouldn't the code run when i = 7? — relentless-coder
– relentless-coder, Commented Oct 1, 2016 at 12:51

Ben Wainwright · Accepted Answer · 2016-10-01 13:12:32Z

1

When i=4, what is the value of count? I think it would be 0, but don't why I am confused about it.

When i == 3, count is set to 0. At the end of the for block, count++ is executed, so by the time i == 4, count == 1

As the code tells, when count = 0, an image will be removed from the body. Does the code append an image, and then remove an image? Or, does it simply remove one image? This is the part that is confusing because nothing is said about what happens when i=3.

i == 0 append
i == 1 append
i == 2 append
i == 3 image from previous step removed
i == 4 append

etc.

edited Oct 1, 2016 at 13:12

answered Oct 1, 2016 at 12:55

Ben Wainwright

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3 Comments

relentless-coder Over a year ago

So, when i=3, does it add an image and then remove it, or does it remove the one that was appended when i =2?

Ben Wainwright Over a year ago

It removes the image that was added in the previous step

Ben Wainwright Over a year ago

@AyushBahuguna I've edited to include that. Could you accept?

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