使用 Lodash 将 JavaScript 数组拆分成块

Question

我需要将 JavaScript 数组拆分为 n 大小的块。

例如：给定这个数组

["a1", "a2", "a3", "a4", "a5", "a6", "a7", "a8", "a9", "a10", "a11", "a12", "a13"]

而n 等于4，输出应该是这样的：

[ ["a1", "a2", "a3", "a4"],
  ["a5", "a6", "a7", "a8"],
  ["a9", "a10", "a11", "a12"],
  ["a13"]
]

我知道纯 JavaScript solutions 可以解决这个问题，但由于我已经在使用 Lodash 我想知道 Lodash 是否为此提供了更好的解决方案。

编辑：

我创建了一个jsPerf test 来检查下划线解决方案的速度有多慢。

Answer 1

看看 lodash' chunk：https://lodash.com/docs#chunk

const data = ["a1", "a2", "a3", "a4", "a5", "a6", "a7", "a8", "a9", "a10", "a11", "a12", "a13"];
const chunks = _.chunk(data, 3);
console.log(chunks);
// [
//  ["a1", "a2", "a3"],
//  ["a4", "a5", "a6"],
//  ["a7", "a8", "a9"],
//  ["a10", "a11", "a12"],
//  ["a13"]
// ]

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

Answer 2

对于基于下划线的解决方案，试试这个：

var data = ["a1", "a2", "a3", "a4", "a5", "a6", "a7", "a8", "a9", "a10", "a11", "a12", "a13"];
var n = 3;
var lists = _.groupBy(data, function(element, index){
  return Math.floor(index/n);
});
lists = _.toArray(lists); //Added this to convert the returned object to an array.
console.log(lists);

使用链式包装方法，您可以将两个语句组合如下：

var data = ["a1", "a2", "a3", "a4", "a5", "a6", "a7", "a8", "a9", "a10", "a11", "a12", "a13"];
var n = 3;
var lists = _.chain(data).groupBy(function(element, index){
  return Math.floor(index/n);
}).toArray()
.value();

Answer 3

一个可能更简单的表达式：

const coll = [ "a1", "a2", "a3", "a4", "a5", "a6", "a7", "a8", "a9" ];
const n = 2;
const chunks = _.range(coll.length / n).map(i => coll.slice(i * n, (i + 1) * n));
console.log(chunks);

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

Answer 4

Underscore 从 1.9.0 版本开始原生支持 _.chunk()。

const data = ["a1", "a2", "a3", "a4", "a5", "a6", "a7", "a8", "a9", "a10", "a11", "a12", "a13"];
const chunks = _.chunk(data, 4);
console.log(chunks);

<script src="https://cdnjs.cloudflare.com/ajax/libs/underscore.js/1.9.1/underscore.js"></script>

Answer 5

试试这个更实用（例如，如果您想根据每个子数组中要成为容器的项目数量来拆分数组）：

function chunk(arr, start, amount){
    var result = [], 
        i, 
        start = start || 0, 
        amount = amount || 500, 
        len = arr.length;

    do {
        //console.log('appending ', start, '-', start + amount, 'of ', len, '.');
        result.push(arr.slice(start, start+amount));
        start += amount;

    } while (start< len);

    return result;
};

在你的情况下使用：

var arr = [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17],
    chunked = chunk(arr, 0, Math.floor(arr.length/3)); //to get 4 nested arrays

console.log(chunked);

还有一个案例：

var arr = [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17],
    chunked = chunk(arr, 0, 3); // to get 6 nested arrays each containing maximum of 3 items

console.log(chunked);