Split JavaScript array in chunks using Lodash

问题

I need to split a JavaScript array into n sized chunks.

E.g.: Given this array

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

and a n equals to 4, the output should be this:

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

I aware of pure JavaScript solutions for this problem, but since I am already using Lodash I am wondering if Lodash provides a better solution for this.

Edit:

I created a jsPerf test to check how much slower the underscore solution is.

回答1:

Take a look at lodash' chunk: https://lodash.com/docs#chunk

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

回答2:

For Underscore based solution try this:

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);

Using the chain wrapper method you can combine the two statements as below:

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();

回答3:

A possibly simpler expression:

    _.range(coll.length / n).map(i => coll.slice(i * n, (i + 1) * n))

回答4:

Underscore supports _.chunk() natively as of version 1.9.0.

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

回答5:

try this one it is much more practical (for example, if you would want to split the array based on amount of items to be container in each sub array):

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;
};

and the use in your case:

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);

and another case:

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);

来源：https://stackoverflow.com/questions/8566667/split-javascript-array-in-chunks-using-lodash