How can an Array have length 0 and 30 at the same time?

Question

I have an array that has length = 0 but when I print it I see 30 entries. Still I can't call the map function on it. What am I dealing with here?

This is the output of from my react function. Not entering anything into the Chrome console and not altering the Array:

console.log(Array.isArray(props.images));
console.log(props.images.length);
console.log(props.images);