API / Js / Dict

Dict

Provide utilities for JS dictionary object.

Note: This module's examples will assume this predeclared dictionary:

Examples

RESCRIPT
let ages = Js.Dict.fromList(list{("Maria", 30), ("Vinh", 22), ("Fred", 49)})

t

RESCRIPT

type t<'a> = dict<'a>

key

RESCRIPT

type key = string

The type for dictionary keys. This means that dictionaries must use strings as their keys.

get

RESCRIPT

let get: (t<'a>, key) => option<'a>

Js.Dict.get(key) returns None if the key is not found in the dictionary, Some(value) otherwise.

Examples

RESCRIPT
Js.Dict.get(ages, "Vinh") == Some(22)
Js.Dict.get(ages, "Paul") == None

unsafeGet

RESCRIPT

let unsafeGet: (t<'a>, key) => 'a

Js.Dict.unsafeGet(key) returns the value if the key exists, otherwise an undefined value is returned. Use this only when you are sure the key exists (i.e. when having used the keys() function to check that the key is valid).

Examples

RESCRIPT
Js.Dict.unsafeGet(ages, "Fred") == 49
Js.Dict.unsafeGet(ages, "Paul") // returns undefined

set

RESCRIPT

let set: (t<'a>, key, 'a) => unit

Js.Dict.set(dict, key, value) sets the key/value in the dictionary dict. If the key does not exist, and entry will be created for it.

This function modifies the original dictionary.

Examples

RESCRIPT
Js.Dict.set(ages, "Maria", 31)
Js.log(ages == Js.Dict.fromList(list{("Maria", 31), ("Vinh", 22), ("Fred", 49)}))

Js.Dict.set(ages, "David", 66)
Js.log(ages == Js.Dict.fromList(list{("Maria", 31), ("Vinh", 22), ("Fred", 49), ("David", 66)}))

keys

RESCRIPT

let keys: t<'a> => array<string>

Returns all the keys in the dictionary dict.

Examples

RESCRIPT
Js.Dict.keys(ages) == ["Maria", "Vinh", "Fred"]

empty

RESCRIPT

let empty: unit => t<'a>

Returns an empty dictionary.

unsafeDeleteKey

RESCRIPT

let unsafeDeleteKey: (t<string>, string) => unit

Experimental internal function

entries

RESCRIPT

let entries: t<'a> => array<(key, 'a)>

Returns an array of key/value pairs in the given dictionary (ES2017).

Examples

RESCRIPT
Js.Dict.entries(ages) == [("Maria", 30), ("Vinh", 22), ("Fred", 49)]

values

RESCRIPT

let values: t<'a> => array<'a>

Returns the values in the given dictionary (ES2017).

Examples

RESCRIPT
Js.Dict.values(ages) == [30, 22, 49]

fromList

RESCRIPT

let fromList: list<(key, 'a)> => t<'a>

Creates a new dictionary containing each (key, value) pair in its list argument.

Examples

RESCRIPT
let capitals = Js.Dict.fromList(list{("Japan", "Tokyo"), ("France", "Paris"), ("Egypt", "Cairo")})

fromArray

RESCRIPT

let fromArray: array<(key, 'a)> => t<'a>

Creates a new dictionary containing each (key, value) pair in its array argument.

Examples

RESCRIPT
let capitals2 = Js.Dict.fromArray([("Germany", "Berlin"), ("Burkina Faso", "Ouagadougou")])

map

RESCRIPT

let map: ('a => 'b, t<'a>) => t<'b>

map(f, dict) maps dict to a new dictionary with the same keys, using the function f to map each value.

Examples

RESCRIPT
let prices = Js.Dict.fromList(list{("pen", 1.00), ("book", 5.00), ("stapler", 7.00)})

let discount = (. price) => price *. 0.90
let salePrices = Js.Dict.map(discount, prices)

salePrices == Js.Dict.fromList(list{("pen", 0.90), ("book", 4.50), ("stapler", 6.30)})