Stumped on this Kata...'Directions Reduction'

JavaScript
9

This is a stack:

var stack = [];

To check the top value of the stack (peek):

var top = stack[stack.length - 1]

push/pop the stack:

stack.pop()
stack.push(value)

Iterate over your array of directions. For each direction, rules are: peek at stack. If value on top of stack + current value in array are N/S or E/W, pop stack. If they aren’t, push the current value in the array to the stack.

This means there is only a single pass, and you don’t need to poke around or manipulate inside the array: the stack will end up having the correct directions in the correct order.

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