Javascript中的数组

快速创建并填充数组

const array = new Array(12).fill(0);
console.log(array); // 输出: [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]

const array = Array.from({ length: 12 }, () => 0);
console.log(array); // 输出: [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]

数组排序

const array = [
    { name: 'Alice', value: 30 },
    { name: 'Bob', value: 20 },
    { name: 'Charlie', value: 25 }
];

// 按照 value 属性从大到小排序（改变原数据）
array.sort((a, b) => b.value - a.value);

数组对象分类

const people = [
    { name: 'tom', age: 17, birthYear: 2021 },
    { name: 'tony', age: 21, birthYear: 2021 },
    { name: 'bob', age: 18, birthYear: 2020 },
    { name: 'bob', age: 18, birthYear: 2021 },
    { name: 'bob', age: 18, birthYear: 2019 },
];

function groupBy(arr, property) {
    if (!Array.isArray(arr)) return [];
    return arr.reduce((pre, obj) => {
        const newObj = {
            [property]: obj[property],
            data: [obj],
        };
        if (!pre.length) {
            return [newObj];
        }
        for (let i = 0; i < pre.length; i++) {
            let item = pre[i];
            if (item[property] === obj[property]) {
                item.data = [...item.data, obj];
                return pre;
            }
        }
        return [...pre, newObj];
    }, []);
}

const value = groupBy(people, 'birthYear');