在控制台中打印数组时长度错误

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