isValidWalk.js

/*
You live in the city of Cartesia where all roads are laid out in a perfect grid. 
You arrived ten minutes too early to an appointment, so you decided to take the 
opportunity to go for a short walk. 

The city provides its citizens with a Walk Generating App on their phones -- 
every time you press the button it sends you an array of one-letter strings representing 
directions to walk (eg. ['n', 's', 'w', 'e']). 

You always walk only a single block for each letter (direction) and you know it 
takes you one minute to traverse one city block, so create a function that will return 
true if the walk the app gives you will take you exactly ten minutes (you don't want to be 
early or late!) and will, of course, return you to your starting point. 

Return false otherwise.

Test.expect(isValidWalk(['n','s','n','s','n','s','n','s','n','s']), 'should return true');
Test.expect(!isValidWalk(['w','e','w','e','w','e','w','e','w','e','w','e']), 'should return false');
Test.expect(!isValidWalk(['w']), 'should return false');
Test.expect(!isValidWalk(['n','n','n','s','n','s','n','s','n','s']), 'should return false');

*/

const isValidWalk = (walk) => {
	const count = (d) => walk.filter((e) => e === d).length
	return (
		walk.length === 10 && count('n') === count('s') && count('e') === count('w')
	)
}