Why the code produces [1, 2], [3, 4], [1, 2], [3, 4], [1, 2], [3, 4]. What happened to the element array [5, 6] ?

Question

var arr = [[1, 2], [3, 4], [5, 6]];

for(var i=0; i < arr.length; i++) {
for(var j=0; j < arr[i].length; j++) {
console.log(arr[j]);
}
}

Though I do understand when the console log is either:
console.log(arr[i]) or console.log(arr[i][j])

Answer 1

for(var i=0; i < arr.length; i++) {
for(var j=0; j < arr[i].length; j++) {
console.log(arr[i][j]);
}
}

Answer 2

Last value of "j" is 1 (it should be 2, your code is wrong, practise on the code I sent…)

Answer 3

Yes! I said that's wrong!… ~_~

Answer 4

To develop @VH answer:

You attempt to access a bidimentional array with an unique index ( even if you iterate through two index variables ), so you log the 'rows' elements with the index of your 'cols' elements ( 'j' iterate over length of 'arr[i]', but next you access arr[j] instead arr[i][j] )...

Answer 5

With arr[i][j] output is: 1 - 2 - 3 - 4 - 5 - 6... one sub-item by one.
With arr[i] output is 1, 2 - 1, 2 - 3, 4 - 3, 4 - 5, 6 - 5, 6... one sub array repeat twice, one per line/output
With arr[j] output is 1, 2 - 3, 4 - 1, 2 - 3, 4 - 1, 2 - 3, 4: because you iterate over the sub arrays, in index range of sub array length ( always two while length of arr is three ), all this 3 times repeated since you too iterate over index range of arr with the 'for' loop over 'i' ^^

Answer 6

@ValentineHacker thanks didn't get u at first, u mean it's ethically bad code after all it's bidirectional iteration yet accessing only one index. Thanks really grateful

Answer 7

I guess you didn't get my question:
I have no problem if the console log is:
console.log(arr[i]) or console.log(arr[i][j])

The problem is console.log(arr[j]), I don't seem to understand why [5, 6] does not print in the result.
I need practical explanation please.

Answer 8

@ValentineHacker I do understand your code very much well the console.log prints 1, 2, 3, 4, 5, 6

replace the console log in your code to
console.log(arr[j])

to get what I mean. Thanks