I'm currently learning js and stumbled upon this to me weird behavior. I probably missing something fundamental here, but i can't find the answer.

I have a function that modifies an array and returns it. If i print that out the original array gets modified, even though it's a constant.

const arr = [5, 9, 7, 1, 8, ];

function test(arr) {
  const strings = ['qwe', 'asd'];
  arr.splice(1, 0, ...strings);
  return arr
}

console.log(test(arr))
console.log(arr)
console.log(test(arr))
console.log(arr)
console.log(test(arr))
console.log(arr)

Output shows that the original array gets bigger everytime. I was expecting that it is the same output everytime.