Currying functions in Javascript

Slides

Demonstrate ability to curry functions

npm install

mocha -w --bail

Do all work in lib/curry-house.js
Resist the urge to open test/curry-spec.js until the end.

expected result

var add4and5 = calculate(4)('+')(5); // 9

calculate should take in a single argument

calculate should return a function that accepts a single argument, and returns a function based on that argument.

• if that argument is '+' or 'add', return a function that takes a single argument that returns the sum of the argument for calculate and the argument for last function to be returned
• if that argument is '-' or 'subtract', return a function that takes a single argument that returns the difference of the argument for calculate and the argument for last function to be returned
• if that argument is '*' or 'multiply', return a function that takes a single argument that returns the product of the argument for calculate and the argument for last function to be returned
• if that argument is '/' or 'divide', return a function that takes a single argument that returns the quotient of the argument for calculate and the argument for last function to be returned
• if that argument is '%' or 'modulo', return a function that takes a single argument that returns the remainder of dividing the argument for calculate and the argument for last function to be returned
• if that argument is '^' or 'power of', return a function that takes a single argument that returns the exponentiation of the argument for calculate to the power of the argument for last function to be returned

expected result

var randomNumberFrom20to25 = random(20).to(25);
// 20,21,22,23 or 24

var randomNumberFrom20 = random(20);
var randomNumberFrom20to25inc = randomNumberFrom20.toInclude(25);
// 20,21,22,23,24 or 25

random should take a single argument start

random should return an object with two keys, to and toInclude

the value of to is a function that takes a single argument end, and returns a whole random number between start and end (exclusive)

the value of toInclude is a function that takes a single argument end, and returns a whole random number between start and end (inclusive)

concat is a function that accepts two arguments, and returns the two arguments as a concatenated string

prependGreeting is a variable with the value set to the function returned by currying (using the curry helper) the concat function, with a hard-coded first argument 'Hello '

expected result

var greeting = prependGreeting('Json'); // 'Hello Json'

add should take 3 arguments and return the sum of all arguments

add4and5 is a variable with it's value set to the function returned by currying (using the curry helper) the add function, with two a hard-coded arguments 4 and 5

expected result

var sumWith4and5 = add4and5(6); // 15

calculator should take in a single argument operation

calculator should return a function that accepts two arguments op2 and op1, and returns a result based on the two arguments.

• if operation is '+' or 'add', returns the sum of op1 added by op2
• if operation is '-' or 'subtract', returns the difference of op1 subtracted by op2
• if operation is '*' or 'multiply', returns the prouduct of op1 multiplied by op2
• if operation is '/' or 'divide', returns the quotient of op1 divided by op2
• if operation is '%' or 'modulo', returns the remainder of op1 divided by op2
• if operation is '^' or 'power of', returns the exponentiation of op1 to the power of op2

add5 is a variable with a value set to the function returned by currying the function returned by invoking calculator with an argument '+', and binding the curried functions first argument to 5

expected result

add5(4); // 9

sub5 is a variable with a value set to the function returned by currying the function returned by invoking calculator with an argument '-', and binding the curried functions first argument to 5

expected result

sub5(4); // -1

multiply5 is a variable with a value set to the function returned by currying the function returned by invoking calculator with an argument '*', and binding the curried functions first argument to 5

expected result

multiply5(4); // 20

divide5 is a variable with a value set to the function returned by currying the function returned by invoking calculator with an argument '/', and binding the curried functions first argument to 5

expected result

divide5(20); // 4

mod5 is a variable with a value set to the function returned by currying the function returned by invoking calculator with an argument '%', and binding the curried functions first argument to 5

expected result

mod5(99); // 4

"99 divided by 5 has remainder 4"

pow3 is a variable with a value set to the function returned by currying the function returned by invoking calculator with an argument '^', and binding the curried functions first argument to 3

expected result

pow3(4); // 64

"4 to the power of 3"

stretch goal, commit to new branch named lo-dash

Replace the curry helper with lo-dash's partial function.