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}))
