Just for references, here are examples of map, filter and reduce in C# and JavaScript. For JavaScript, Iā€™m using RamdaJS.

Map

new int[] {3, 4, 5}.Select(x => x * 3);
R.map(x => x * 3, [3,4,5])

Filter

new int[] {3, 4, 5,6}.Where(x => x % 2 == 0);
R.filter(x => x % 2 === 0, [3,4,5,6])

Reduce

new int[] {3, 4, 5,6}.Aggregate(0, (acc, x) => acc + x);
new int[] {3, 4, 5,6}.Aggregate(0, (acc, x) => acc + x);