smaller lodash.isEqual

_.isEqual.coffee

__toString = Object.prototype.toString

isEqual = (a, b) ->
  if arguments.length < 2
    return false # cannot compare

  typeA = typeOf(a)
  typeB = typeOf(b)

  # falsy values can be compared by reference except for NaN
  # NOTE: window.isNaN fails for isNaN("NaN"), Number.isNaN is not supported in IE11
  # source: http://kangax.github.io/compat-table/es6/#test-Number.isNaN
  if !a or !b 
    return a == b or (typeA == 'number' and isNaN(a) and isNaN(b))

  # truthy primitives can be compared by reference
  if isPrimitive(a) or isPrimitive(b)
    return a == b

  # regexps are other kind of... thing (no keys, no way to compare on the loop below)
  if typeA == 'regexp' or typeB == 'regexp'
    return a.toString?() == b.toString?()

  # "a" and "b" are objects (compare recursively)
  for keyA, valueA of a
    if !isEqual(b[keyA], valueA)
      return false

  return true

typeOf = (value) ->
  return __toString.call(value).match(/(\w+)\]/).pop();

isPrimitive = (value) ->
  return false if arguments.length < 1
  return /undefined|null|string|number|boolean|symbol/i.test(
    typeOf(value)
  )