Can someone pls explain why this code is outputting 12 ?

Question

var arr = [1, 2, 3, 4];
var length = arr.length;
for(var i =0; i < length; i++) {
length--;
document.write(arr[i]);
}

Answer 1

The loop runs 2 times because the length variable is changed 2 times and its value at the end of the second iteration is 2.

Answer 2

Lara, please, stop being lazy, I gave you a great tool for step-by-step tracking of code execution. take advantage of it! try to do most of the work yourself

Answer 3

Hey, I'm not being lazy before i asked the question, i tried solving it with python Tutor but I'm still confused :( . I understand the initial length is 4 then length-- is 3, was 12 gotten by multiplying both values or wah?
Damn JavaScript gives me headache and always makes me feel dump. I really don't know what to do to help me understand JS but i won't give up.

Answer 4

Lara

length = 4;

for (i = 0; i < length; i++)

After this iteration length will be increment by 1 so length will be 3 and a[0] will be 1

Now your 2nd iteration will look like this:

for (i = 1; i < 3; i++) after this iteration length will be 2 and a[1] will be 2

Now your 3rd iteration will look like this:

for (i = 2; i < 2; i++) now this will not execute because of 2 < 2 false

So your final result will be 12