kata2.js

/*
This time we want to write calculations using functions and get the results. Let's have a look at some examples:

seven(times(five())); // must return 35
four(plus(nine())); // must return 13
eight(minus(three())); // must return 5
six(dividedBy(two())); // must return 3

There must be a function for each number from 0 ("zero") to 9 ("nine")
There must be a function for each of the following mathematical operations: plus, minus, times, dividedBy (divided_by in Ruby)
Each calculation consist of exactly one operation and two numbers
The most outer function represents the left operand, the most inner function represents the right operand

*/

function zero(fn)     { return fn ? fn(0) : 0; }
function one(fn)      { return fn ? fn(1) : 1; }
function two(fn)      { return fn ? fn(2) : 2; }
function three(fn)    { return fn ? fn(3) : 3; }
function four(fn)     { return fn ? fn(4) : 4; }
function five(fn)     { return fn ? fn(5) : 5; }
function six(fn)      { return fn ? fn(6) : 6; }
function seven(fn)    { return fn ? fn(7) : 7; }
function eight(fn)    { return fn ? fn(8) : 8; }
function nine(fn)     { return fn ? fn(9) : 9; }
function plus(number)  { return function(a) { return a + number; } }
function minus(number) { return function(a) { return a - number; } }
function times(number) { return function(a) { return a * number; } }
function dividedBy(number) { return function(a) { return a / number; } }