I don't fully understand how the code works?

Question

JavaScript

Hello everyone. I don't fully understand how this code works. Explain, please. Task from Codewars:

function dirReduc(plan) {
  var opposite = {
    'NORTH': 'SOUTH', 'EAST': 'WEST', 'SOUTH': 'NORTH', 'WEST': 'EAST'};
  return plan.reduce(function(dirs, dir){
      if (dirs[dirs.length - 1] === opposite[dir])
        dirs.pop();
      else
        dirs.push(dir);
      return dirs;
    }, []);
}
dirReduc(["NORTH", "SOUTH", "SOUTH", "EAST", "WEST", "NORTH", "WEST"]);

Answer 1

All neighboring elements denoting opposite directions are removed from the array.