Split JavaScript array in chunks using Lodash
Solution 1
Take a look at 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>
Solution 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();
Solution 3
Underscore supports _.chunk() natively as of version 1.9.0.
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>
Solution 4
A possibly simpler expression:
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>
Solution 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);
Comments
-
Cesar Canassa over 3 years
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.