initialValue在javascript reduce函数中是如何工作的？

const numbers = [1, 2, 3, 4, 5];

// 求和
const sum = numbers.reduce((accumulator, currentValue) => accumulator + currentValue, 0);
console.log(sum); // 输出：15

// 求积
const product = numbers.reduce((accumulator, currentValue) => accumulator * currentValue, 1);
console.log(product); // 输出：120

// 查找最大值
const max = numbers.reduce((accumulator, currentValue) => Math.max(accumulator, currentValue), -Infinity);
console.log(max); // 输出：5

// 数组转换为对象
const names = ['Alice', 'Bob', 'Charlie'];
const nameAgeMap = names.reduce((accumulator, currentValue, currentIndex) => {
  accumulator[currentValue] = currentIndex + 20; // 假设年龄是索引加20
  return accumulator;
}, {});
console.log(nameAgeMap); // 输出：{ Alice: 20, Bob: 21, Charlie: 22 }

const emptyArray = [];

// 提供 initialValue
const sumEmpty = emptyArray.reduce((accumulator, currentValue) => accumulator + currentValue, 0);
console.log(sumEmpty); // 输出：0

// 检查数组是否为空
if (emptyArray.length > 0) {
  const sum = emptyArray.reduce((accumulator, currentValue) => accumulator + currentValue);
  console.log(sum);
} else {
  console.log('Array is empty');
}