Getting a wrong length when printing an array in console

Question

When doing a console.log of an array, I get the following results:

What does the number (25) represent in the first picture (at the top)? My array has a length of 27, not 25. I thought it was the count of non-null values, but the second picture tells otherwise.

The (25) and (27) are also present in the reduced form:

This happens in both Firefox and Chrome.

The code that leads to this behaviour:

var lows = ts2values[current_ts];
var highs = ts2values[current_ts];

console.log("lows b : ", lows);
console.log("highs b : ", highs);

lows.push(null);
highs.push(null);

console.log("lows a : ", lows);
console.log("highs a : ", highs);

Answer 1

What does the number (25) represent in the first picture (at the top)?

The length of the array at that time.

You can see the same result by the following code.

myArray = [1, 2, 3]
console.log(myArray)

myArray.push(4, 5, 6)
console.log(myArray)

the first log is Array(3)

and expanding the first log, the length of the array is 6, not 3 because it was updated after console.log