用 object 的 key 对 array of objects 进行分组

groupByKeys.js

const list = [
  { province: '天津', city: '南开', district: '三马路' },
  {
    province: '天津',
    city: '南开',
    district: '四马路'
  },
  {
    province: '天津',
    city: '河西',
    district: '二马路'
  },
	{
		province: '江苏省',
		city: '无锡市',
		district: '新吴区'
	},
	{
		province: '江苏省',
		city: '无锡市',
		district: '无锡经济开发区'
	}
]

function omitKeys(obj, keys) {
  const cloned = JSON.parse(JSON.stringify(obj));
  keys.forEach(key => {
    delete cloned[key];
  })
  return cloned;
}


function liftPropsAsKeys(obj, props) {
	if (props.length < 1) {
		return obj;
	}
	const [prop, ...restProps]= props;
	if (props.length === 1) {
		return {
			[obj[prop]]: omitKeys(obj, [prop])
		}
	}
	return {
		[obj[prop]]: liftPropsAsKeys(omitKeys(obj, [prop]), restProps)
	}
}

// const obj = { age: 10, name: 'Jason', address: 'Baker Street', sex: 'Male' }
// const lifted = liftPropsAsKeys(obj, ['age', 'name', 'sex']);
// console.log(JSON.stringify(lifted, null, 2))

function groupByKeys(list, props) {
	if (props.length === 0) {
		return list;
	}
	const result = [];
	const [prop, ...restProps] = props;
	list.forEach(li => {
		const lifted = liftPropsAsKeys(li, [prop]);
		const key = li[prop];
		const value = lifted[key];
		// 特殊处理：如果 key 对应的 value 是空对象的话，直接使用 key 作为 value
		if (Object.keys(value).length === 0) {
			if (!result.includes(key)) {
				result.push(key)	
			}
			return;
		}
		// 普通 group by 处理 
		lifted[key] = [value];
		const itemWithSameKey = result.find(it => Object.keys(it).includes(key));
		if (itemWithSameKey) {
			itemWithSameKey[key].push(value);
		} else {
			result.push(lifted)
		}
	})
	result.forEach(li => {
		Object.keys(li).forEach(key => {
			li[key] = groupByKeys(li[key], restProps)
		})
	})
	return result;
}

const groupedList = groupByKeys(list, ['province', 'city', 'district']);

console.log(JSON.stringify(groupedList, null, 2));