我不能正确理解递归函数是如何工作的

function rangeOfNumbers(startNum, endNum) {
  if (startNum === endNum) {
    let arr = [startNum];
    console.log('result of call with startNum:', startNum, ', endNum:', endNum, arr);
    return arr;
  } else if (startNum > endNum) { 
    return; 
  } else {
    let arr = rangeOfNumbers(startNum + 1, endNum);
    console.log('result of recursive call with startNum + 1:', startNum + 1, ', endNum:', endNum, arr);
    arr.unshift(startNum);
    console.log('after adding startNum to beginning of array:', startNum, arr);
    console.log('result of call with startNum:', startNum, ', endNum:', endNum, arr);
    return arr;
  }
};

console.log('final result', rangeOfNumbers(0, 4));

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