JavaScript reduce 方法详解：累计计算、对象分组与数组展平

const arr = [12, 3, 7, 34, 6, 22, 15];
const total = arr.reduce((acc, cur) => acc + cur, 0);
console.log(total); // 99

const people = [
    { name: "Alice", age: 21 },
    { name: "Max", age: 20 },
    { name: "Jane", age: 20 }
];
const ages = people.reduce((acc, cur) => acc + cur.age, 0);
console.log(ages); // 61

const people = [
    { name: "Alice", age: 21 },
    { name: "Max", age: 20 },
    { name: "Jane", age: 20 }
];

const ageGroups = people.reduce((acc, cur) => {
    const age = cur.age;
    if (!acc[age]) {
        acc[age] = [];
    }
    acc[age].push(cur.name);
    return acc;
}, {});
console.log(ageGroups);
// {
//     20: ["Max", "Jane"],
//     21: ["Alice"]
// }

const arr = [
    [0, 1],
    [2, 3],
    [4, 5, 6,7]
];
const flattenArr = arr.reduce((acc, cur) => acc.concat(cur), []);
console.log(flattenArr);
// [0, 1, 2, 3, 4, 5, 6, 7]