directionsReduction.js

const opposite = {
  'NORTH': 'SOUTH', 
  'SOUTH': 'NORTH', 
  'EAST': 'WEST', 
  'WEST': 'EAST'
};

function dirReduc(arr) { 
  let hasReduced = false
  let newArray = []
  
  arr.forEach((actual, i, a) => {
    if(hasReduced) return
    const next = a[i+1];
    
    if(!next) return 
    
    if(opposite[actual] === next) {
      hasReduced = true
      newArray = [...a.slice(0, i), ...a.slice(i+2)]
    }
    
  })
  
  if(hasReduced) {
    return dirReduc(newArray)
  }
  
  return arr
}