how to split array into n groups? (factorize, or _

Question

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• Partitioning in JavaScript [duplicate] 7 answers

Let's say I have an array = [0,1,2,3,4,5,6] and I want to "partition" it into 3 arrays, based on reminder after division by 3.

so basically I'd want something like:

_.my_partition([0,1,2,3,4,5,6], function(item) {return item % 3;})
// [[0,3,6], [1,4],[2,5]]

(I can use lodash, underscore, if ti helps...)

Answer 1

There are multiple to do this:

I. Normal function

function partition(items, n) {
    var result = _.groupBy(items, function(item, i) {
        return Math.floor(i % n);
    });
    return _.values(result);
}

myArray = [1,2,3,4,5,6,7,8,9,10];
partition(myArray, 3);

II. Adding a prototype method

Array.prototype.partition = function(n) {
    var result = _.groupBy(this, function(item, i) {
        return Math.floor(i % n);
    });
    return _.values(result);
}

myArray = [1,2,3,4,5,6,7,8,9,10];
myArray.partition(3)

Create an _.partitionToGroups method

_.partitionToGroups = function(items, n) {
    var result = _.groupBy(items, function(item, i) {
        return Math.floor(i % n);
    });
    return _.values(result);
}

myArray = [1,2,3,4,5,6,7,8,9,10];
_.partitionToGroups(myArray, 3);