标签：el group name sex score 分组 key values JS

扩展数组方法

Array.prototype.groupBy = function groupBy(key) {     const hash = {},         result = [];     for (const el of this) {         if (hash[el[key]]) {             hash[el[key]].push(el);         } else {             result.push({                 key: el[key],                 values: (hash[el[key]] = [el]),             });         }     }     return result; };
Array.prototype.key = function (key) {     return this.map(el => el[key]); };
Array.prototype.sum = function (key) {     return this.reduce((total, el) => total + (key ? el[key] : el), 0); };
Array.prototype.distinct = function () {     return [...new Set(this)]; };

示例

let arr = [
    { name: 'Tom', sex: 'male', score: 95 },
    { name: 'Alice', sex: 'female', score: 85 },
    { name: 'Bill', sex: 'male', score: 58 },
    { name: 'Jack', sex: 'male', score: 63 },
    { name: 'Mary', sex: 'female', score: 77 },
];

# 按性别分组计算总分
arr.groupBy('sex').map(({key,values})=>({'sex':key,'sum':values.sum('score')}))

# 按性别分组计算人数
arr.groupBy('sex').map(({key,values})=>({'sex':key,'sum':values.length}))

 

 

标签：el,group,name,sex,score,分组,key,values,JS
From： https://www.cnblogs.com/whjblog/p/17359817.html