rename error-handling.js to chapter5.js
rename funct-programming.js to chapter6.js
create array of road objects
make a function makeRoads
add a function roadFrom()
add a function gamblerPath()
add a function member()
adjust forEach to recognise a certain kind of exceptions
add a function every()
add a function flatten() that takes an array of arrays
add a function filter
add a function that returns an array of route objects
add a function minimize
add a function weightedDistance
add a objects containing x and y properties
add a function possibleDirections which takes a point object as argument and returns an array
add a function identity
add a function estimatedDistance
create a method BinaryHeap
add codes to pass multiple routes to showRoute