split-object

split-object

Minimal tool for working with Objects using built-in functional Array methods.

split-object will split an Object into an Array of keys & values, allowing you to manipulate the Object using Array methods then join values back into an Object.

In comparison to for..in or Object.keys().forEach() an Array of the form [{key1: value1}, {key2: value2}] can be a far more natural & convenient structure to work with.

split-object has both a split and a join method, similar to how String#split/Array#join combine to convert back & forward between Strings & Arrays.

Post ES6 we might see some better methods for iterating over Objects.

Installation

npm install split-object

Usage

var salad = {
  apples: 1,
  bananas: 3,
  carrots: 2
}

// transform each key/value using Array.prototype.map
var loudIngredients = split(salad).map(function(ingredient) {
  ingredient.key = ingredient.key.toUpperCase()
  ingredient.value *= 3
  return ingredient
})

// loudIngredients:
// [
//   { key: 'APPLES', value: 3 },
//   { key: 'BANANAS', value: 9 },
//   { key: 'CARROTS', value: 6 }
// ]

var loudSalad = split.join(loudIngredients)

// loudSalad:
// {
//    APPLES: 3,
//    BANANAS: 9,
//    CARROTS: 6
// }
//

Examples

Iterating Keys & Values

// with object-split
split(salad).forEach(function(item) {
  console.log(item.key, item.value)
})

// without object-split
Object.keys(salad).forEach(function(key) {
  var value = salad[key]
  console.log(key, value)
})

// or
for (var key in salad) {
  var value = salad[key]
  console.log(key, value)
}

Chaining Transformations

// with object-split
var pieces = split(salad)
.map(function(kv) {
  kv.value = calculate(kv.value)
  return kv
})
.map(function(kv) {
  kv.value = recalculate(kv.value)
  return kv
})
var newSalad = split.join(pieces)

Without splitting the Object into a similar structure to split-object, you're stuck with losing the keys (which is acceptable if you can deduce keys from the value) or using multiple reduce calls/for..of iteration:

// without object-split
var newSalad = Object.keys(salad)
.reduce(function(obj, key) {
  var value = salad[key]
  obj[key] = calculate(value)
  return obj
}, {})
newSalad = Object.keys(newSalad)
.reduce(function(obj, key) {
  var value = newSalad[key]
  obj[key] = recalculate(value)
  return obj
}, {})

split-object doesn't save a huge number of lines, but it saves some complexity, enables easier chaining and removes the hassle of extracting the value from the object on each iteration.

Custom Key/Value Names

To provide more semantic key/value names, supply a second argument to either split or join with the key/value mapping:

var salad = {
  apples: 1,
  bananas: 3,
  carrots: 2
}

var loudIngredients = split(salad, {key: 'name', value: 'amount'}).map(function(ingredient) {
  ingredient.name = ingredient.name.toUpperCase()
  ingredient.amount *= 3
  return ingredient
})

// loudIngredients:
// [
//   { name: 'APPLES', amount: 3 },
//   { name: 'BANANAS', amount: 9 },
//   { name: 'CARROTS', amount: 6 }
// ]

var loudSalad = split.join(loudIngredients, {key: 'name', value: 'amount'})

// loudSalad:
// {
//    APPLES: 3,
//    BANANAS: 9,
//    CARROTS: 6
// }
//

This also means you can use join to create an Object out of any Array of Objects with two properties.

Remember to also supply the mapping to join otherwise it won't be able to find the correct key/value pair to re-form the object.

See Also

• hughsk/flat – Flatten/unflatten nested Javascript objects (Highly recommended for use with split-object).

License

MIT