如何使用 lodash 或 javascript 按数组分组

Question

一个数组如下：let names = [             'Aditya',             'Aditya',             'Aditya',             'Abhi',             'Abhi',             'goyal'            ]我想使用 lodash 函数并转换将返回我的名称数组[  Aditya(3),  Abhi(2),  goyal(1)]

Answer 1

您可以使用_.countBy()来获取带有计数的名称对象，或者_.groupBy()如果您想要带有数组的名称对象。

使用_.groupBy()and的数组数组_.values()：

const names = ["Aditya","Aditya","Aditya","Abhi","Abhi","goyal"]

const result = _.values(_.groupBy(names))

console.log(result)

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.15/lodash.js"></script>

和计数的对象_.countBy：

const names = ["Aditya","Aditya","Aditya","Abhi","Abhi","goyal"]

const result = _.countBy(names)

console.log(result)

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.15/lodash.js"></script>

更新 - 要获取组合键和值的字符串数组，您可以使用_.countBy()，然后使用_.map()它（lodash 也_.map()适用于对象）。

const names = ["Aditya","Aditya","Aditya","Abhi","Abhi","goyal"]

const result = _.map(_.countBy(names), (v, k) => `${k}(${v})`)

console.log(result)

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.15/lodash.js"></script>

Answer 2

1)_.countBy生成对象的名称，名称/计数作为键/值。

2)_.entries用于将对象转换为一组嵌套条目数组。

3）_.map在条目上产生所需的输出。

const names = ["Aditya","Aditya","Aditya","Abhi","Abhi","goyal"]

const toString = ([name, count]) => `${name}(${count})`;

const entries = _.entries(_.countBy(names));

const result = _.map(entries, toString);

console.log(result);

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.15/lodash.js"></script>

另外，您可以用香草JS实现使用（几乎）相同数量的代码同样的事情reduce，Object.entries和map。

const names = ["Aditya","Aditya","Aditya","Abhi","Abhi","goyal"]

const counts = names.reduce((acc, c) => {

  return acc[c] = (acc[c] || 0) + 1, acc;

}, {});

const toString = ([name, count]) => `${name}(${count})`;

const entries = Object.entries(counts);

const result2 = entries.map(toString);

console.log(result2);