01:代替map和filter
const arr = [0, 1, 2, 3];
// 代替map：[0, 2, 4, 6]
const arrA = arr.map(item => item * 2);
const arrB = arr.reduce((items, item) => {
return [...items, item * 2]
}, []);
// 代替filter：[2, 3]
const A = arr.filter(item => {
return item > 1
});
const B = arr.reduce((items, item) => {
return item > 1 ? [...items, item] : t
}, []);
// 代替map和filter：[4, 6]
const C = arr.map(item => {
return item * 2
}).filter(item => {
return item > 2
});
const D = arr.reduce((items, item) => {
return item * 2 > 2 ? [...items, item * 2] : items
}, []);
02:数组分割
function Chunk(arr = [], size = 1) {
return arr.length ? arr.reduce((items, item) => {
return items[items.length - 1].length === size
? items.push([item]) : items[items.length - 1].push(item)
, items
}, [[]])
: [];
}
const arr = [1, 2, 3, 4, 5];
Chunk(arr, 2);
// [[1, 2], [3, 4], [5]]
03:数组过滤
function Difference(arr = [], oarr = []) {
return arr.reduce((items, item) => {
return (!oarr.includes(item) && items.push(item), items)
}, []);
}
const arr1 = [1, 2, 3, 4, 5];
const arr2 = [2, 3, 6]
Difference(arr1, arr2);
// [1, 4, 5]
04:数组填充
function Fill(arr=[],val="",start=0,end=arr.length) {
if (start < 0 || start >= end || end > arr.length){
return arr
};
return [
...arr.slice(0, start),
...arr.slice(start, end).reduce((items, item) => {
return (items.push(val || item), items)
}, []),
...arr.slice(end, arr.length)
];
}
const arr = [0, 1, 2, 3, 4, 5, 6];
Fill(arr, "aaa", 2, 5);
// [0, 1, "aaa", "aaa", "aaa", 5, 6]
05:数组扁平
function Flat(arr = []) {
return arr.reduce((items, item) => {
return items.concat(
Array.isArray(item) ? Flat(item) : item
)
}, [])
}
06:数组去重
function Uniq(arr = []) {
return arr.reduce((items, item) => {
return items.includes(item) ? items : [...items, item]
,[]
});
}
const arr = [2, 1, 0, 3, 2, 1, 2];
Uniq(arr); // [2, 1, 0, 3]
08:数组最大最小值
function Max(arr = []) {
return arr.reduce((items, item) => {
return items > item ? items : item
});
}
function Min(arr = []) {
return arr.reduce((items, item) => {
return items < item ? items : item
});
}
const arr = [12, 45, 21, 65, 38, 76, 108, 43];
Max(arr); // 108
Min(arr); // 12
09:数组成员独立拆解
function Unzip(arr = []) {
return arr.reduce(
(items, item) => (item.forEach((w, i) => items[i].push(w)), items),
Array.from({ length: Math.max(...arr.map(item => item.length)) }).map(v => [])
);
}
const arr = [["a", 1, true], ["b", 2, false]];
Unzip(arr);
// [["a", "b"], [1, 2], [true, false]]
10:对数组成员个数进行统计
此方法是字符统计和单词统计的原理，入参时把字符串处理成数组即可
function Count(arr = []) {
return arr.reduce((items, item) => {
return items[item] = (items[item] || 0) + 1, items
}, {});
}
const arr = [0, 1, 1, 2, 2, 2];
Count(arr);
// { 0: 1, 1: 2, 2: 3 }
11:对数组成员特性进行分组
function Group(arr = [], key) {
return key ? arr.reduce((t, v) => (
!t[v[key]] && (t[v[key]] = []), t[v[key]].push(v), t
), {}) : {};
}
const arr = [
{ area: "GZ", name: "YZW", age: 27 },
{ area: "GZ", name: "TYJ", age: 25 },
{ area: "SZ", name: "AAA", age: 23 },
{ area: "FS", name: "BBB", age: 21 },
{ area: "SZ", name: "CCC", age: 19 }
];
// 以地区area作为分组依据
Group(arr, "area");
//{ GZ: Array(2), SZ: Array(2), FS: Array(1) }
12:对数组成员包含的关键字进行统计
function Keyword(arr = [], keys = []) {
return keys.reduce((t, v) => (
arr.some(w => w.includes(v)) && t.push(v), t),
[]);
}
const text = [
"今天天气真好，我想出去钓鱼",
"我一边看电视，一边写作业",
"小明喜欢同桌的小红，又喜欢后桌的小君，真TM花心",
"最近上班喜欢摸鱼的人实在太多了，代码不好好写，在想入非非"
];
const keyword = ["偷懒", "喜欢", "睡觉", "摸鱼", "真好", "一边", "明天"];
Keyword(text, keyword);
// ["喜欢", "摸鱼", "真好", "一边"]
13:字符串翻转
function ReverseStr(str = "") {
return str.split("").reduceRight((items, item) => items + item);
}
const str = "reduce最牛逼";
ReverseStr(str);
// "逼牛最ecuder"
14:累加累乘
function Accumulation(...vals) {
return vals.reduce((t, v) => t + v, 0);
}
function Multiplication(...vals) {
return vals.reduce((t, v) => t * v, 1);
}
Accumulation(1, 2, 3, 4, 5); // 15
Multiplication(1, 2, 3, 4, 5); // 120
15：权重求和
const scores = [
{ score: 90, subject: "chinese", weight: 0.5 },
{ score: 95, subject: "math", weight: 0.3 },
{ score: 85, subject: "english", weight: 0.2 }
];
const result = scores.reduce((t, v) => t + v.score * v.weight, 0);
16:返回对象指定的键值 function GetKeys(obj = {}, keys = []) { return Object.keys(obj).reduce((items, item) => ( keys.includes(item) && (items[item] = obj[item]), items ), {}); } const target = { a: 1, b: 2, c: 3, d: 4 }; const keyword = ["a", "d"]; GetKeys(target, keyword); // { a: 1, d: 4 }