when to use reduce and reduceRight?

Question

Can you describe this for me?

var arr, total;
arr = [1, 2, 3, 4, 5];
total = arr.reduce(function(previous, current) {
return previous + current;
});
// total         


        

Answer 1

ReduceRight is different from reduce method as it starts computation on values from right to left.

Reference: http://www.thesstech.com/javascript/array_redcueright_method

Reduce Example:

Starting from left to right: 1*2 = 2*3 = 6 * 4 = 24

Ref:http://www.thesstech.com/tryme?filename=javascript_array_reduce_method

ReduceRight Example

Starting from right to left: 1024/256 = 4/4 = 1

Ref:http://www.thesstech.com/tryme?filename=javascript_array_reduceright_method