JSFiddle - React, Tailwind, and code Playground

HTML

<script src="http://underscorejs.org/underscore.js"></script>

CoffeeScript

a = [1,2,3,4,5,6,7,8,9]

partition = (items, size) ->
    groups = _.groupBy items,
                       (it, idx) -> Math.floor(idx/size)
    return _.map groups, (val) -> val
    
console.log (partition a, 3)