Deep Merge

deep-merge.coffee

assert = require('assert')

# Deep merge
#
# - Write a function that takes two objects and returns a new object containing
#   the keys and values from both objects
# - Neither input should be modified
# - If the key exists in both objects...
#   ...merge the values if they are both objects
#   ...give the values in the second object (b) precedence otherwise

isObject = (o) ->
  o && o.constructor == Object

merge = (a, b) ->
  # TODO

# Test input
a =
  hello: "who?"
  foo:
    bar: 1
  first: true

b =
  hello: "world!"
  foo:
    baz: 2
  second: false

# Test that the merge gives us the expected results
assert.deepEqual merge(a, b),
  hello: "world!"
  foo:
    bar: 1
    baz: 2
  first: true
  second: false

# Test that we have not modified the input
assert.deepEqual a,
  hello: "who?"
  foo:
    bar: 1
  first: true

assert.deepEqual b,
  hello: "world!"
  foo:
    baz: 2
  second: false

console.log("All tests pass!")

deep-merge.js

var assert = require('assert');

// Deep merge
//
// - Write a function that takes two objects and returns a new object containing
//   the keys and values from both objects
// - Neither input should be modified
// - If the key exists in both objects...
//   ...merge the values if they are both objects
//   ...give the values in the second object (b) precedence otherwise

var isObject = function(o){
  return o && o.constructor === Object;
};

var merge = function(a, b){
  // TODO
};

// Test input
var a = {
  hello: "who?",
  foo: {
    bar: 1,
  },
  first: true,
};

var b = {
  hello: "world!",
  foo: {
    baz: 2,
  },
  second: false,
};

// Test that the merge gives us the expected results
assert.deepEqual(merge(a, b), {
  hello: "world!",
  foo: {
    bar: 1,
    baz: 2,
  },
  first: true,
  second: false,
});

// Test that we have not modified the input
assert.deepEqual(a, {
  hello: "who?",
  foo: {
    bar: 1,
  },
  first: true,
});

assert.deepEqual(b, {
  hello: "world!",
  foo: {
    baz: 2,
  },
  second: false,
});

console.log("All tests pass!");