How to convert a file into an array line by line in bash

Question

I have a file which is created with

touch hello
echo "apple" >> hello
echo "pear" >> hello
echo "pineapple" >> hello

And I'd like to convert this hello file into an array line by line in bash. I.e. the desired array should have

echo ${arr[1]} // apple
echo ${arr[2]} // pear
echo ${arr[3]} // pineapple

I tried

ARR=( )
function test() {
      fileItemString=$(cat hello |tr "\n" " ")
      ARR+=($fileItemString)
}
test

But it just saves the whole file into the first element of ARR.