How would you implement the Cartesian product of multiple arrays in JavaScript?
As an example,
cartesian([1, 2], [10, 20], [100, 200, 300])
should return
[
[1, 10, 100],
[1, 10, 200],
[1, 10, 300],
[2, 10, 100],
[2, 10, 200]
...
]
Here is a functional solution to the problem (without any mutable variable!) using reduce and flatten, provided by underscore.js:
function cartesianProductOf() {
return _.reduce(arguments, function(a, b) {
return _.flatten(_.map(a, function(x) {
return _.map(b, function(y) {
return x.concat([y]);
});
}), true);
}, [ [] ]);
}
// [[1,3,a],[1,3,b],[1,4,a],[1,4,b],[2,3,a],[2,3,b],[2,4,a],[2,4,b]]
console.log(cartesianProductOf([1, 2], [3, 4], ['a'])); <script src=https://cdnjs.cloudflare.com/ajax/libs/underscore.js/1.9.1/underscore.js></script>Remark: This solution was inspired by http://cwestblog.com/2011/05/02/cartesian-product-of-multiple-arrays/
