JavaScript variable changes inside for loop

Question

i have this for loop:

for (var i = 0; i < pictures.length; i++) {
    var mod = i % 4;
    alert(mod); // first
    //get the current row
    if (mod == 0)
    {
        alert(mod); //second
        tableBody.innerHTML += "<tr>";
    }
    tableBody.innerHTML += "<td><img style='width:146px; height:146px;' src='" + pictures[i].source + "'></td>";
    if (mod == 0)
        tableBody.innerHTML += "</tr>";
}

how come my first alert shows the result of the math calculation inside "mod" variable, and the second alert show always zero ??

Because your 2nd alert is within an if (mod == 0) statement... — Jon
– Jon, Commented Feb 2, 2014 at 10:10

HasanAboShally · Accepted Answer · 2014-02-02 10:08:58Z

2

Because you execute the second alert if and only if mod == 0.

answered Feb 2, 2014 at 10:08

HasanAboShally

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2 Comments

Asaf Nevo Over a year ago

you are right, but it does enter my if statement event when its not == 0

HasanAboShally Over a year ago

you are welcome @AsafNevo :) also I think it's better to use === here instead of == (although it doesn't matter much here, but it's more conventional). Please consider marking as accepted answer if you see it so. tnx

dougajmcdonald · Accepted Answer · 2014-02-02 10:09:07Z

0

The second alert will show 0 because you have it inside an if() statement which checks if mod == 0

answered Feb 2, 2014 at 10:09

dougajmcdonald

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Comments

user2804021 · Accepted Answer · 2014-02-02 10:16:04Z

0

C'mon your second alert is inside if() statement. It will get executed only when mod=0. If mod=0, it will enter if loop and execute the statements there. Your if statement contains alert(mod). So, it will print the value of mod which is equal to zero. And in your first alert, it will calculate the value of mod and will print whatever is the value of variable mod(irrsepective of the fact whether it is zero).

answered Feb 2, 2014 at 10:16

user2804021

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