什么是reduce
const array1 = [1, 2, 3, 4];
const reducer = (accumulator, currentValue) => accumulator
+ currentValue;
// 1 + 2 + 3 + 4
console.log(array1.reduce(reducer));
// expected output: 10
// 5 + 1 + 2 + 3 + 4
console.log(array1.reduce(reducer, 5));
// expected output: 15
reduce() 方法接收一个函数作为累加器,数组中的每个值(从左到右)开始缩减,最终计算为一个值。