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Json.Encode

Turn JSON values into Rescript values

Encoding​

value​

type value = Js.Json.t

Represents a JavaScript value. Alias to Json.value;

encode​

let encode: (value, ~indentLevel: int) => string

Convert a [value] into a prettified string. From here, you can send it as part of an HTTP request, send to Javascript with an exeternal, or anything else! The world is your oyster.

let maria: value =
  object([
    ("name", "Maria"),
    ("age", 26),
  ])

encode(maria, 0) == "{"name":"Maria","age":26}"

encode(maria, 4) ==
"""{
    "name": "Maria",
    "age": 26
}"""

Primatives​

string​

let string: string => value

Turn a string into a Rescript value.

string("")->encode(~indentLevel=0)      == ""
string("abc")->encode(~indentLevel=0)   == "abc"
string("hello")->encode(~indentLevel=0) == "hello"

int​

let int: int => value

Turn an int into a Rescript value.

int(42)->encode(~indentLevel=0) == "42"
int(-7)->encode(~indentLevel=0) == "-7"
int(0)->encode(~indentLevel=0)  == "0"

float​

let float: float => value

Turn a float into a Rescript value.

float(3.14)->encode(~indentLevel=0)           == "3.14"
float(1.618)->encode(~indentLevel=0)          == "1.618"
float(-42)->encode(~indentLevel=0)            == "-42"
float(Js.Float._NaN)->encode(~indentLevel=0)  == "null"
float(infinity)->encode(~indentLevel=0)       == "null"

bool​

let bool: bool => value

Turn a bool into a Rescript value.

bool(true)->encode(~indentLevel=0)  == "true"
bool(false)->encode(~indentLevel=0) == "false"

null​

let null: value

Create a null JSON value

  null->encode(~indentLevel=0) == "null"

Arrays​

array​

let array: (array<'i>, 'i => value) => value

Turn an array into a JSON array.

array([1, 2, 3], int)->encode(~indentLevel=0)         == "[1,2,3]"
array([true, false], bool)->encode(~indentLevel=0)    == "[true,false]"
array(["a", "b"], string)->encode(~indentLevel=0)     == "[\"a\",\"b\"]"

What if you need to encode your Rescript into a heterogeneous JSON array, like [1, "hey"]? Modeling your JSON like this is generally a bad idea. Unfortunately, we sometimes have to send JSON/JavaScript to places outside our control. If this is the case for you, can use array like so:

[int(1), string("Hey")]
  ->array(v => v)
  ->encode(~indentLevel=0)
  == "[1,\"Hey\"]"

In Rescript, you can't have an array of heterogenous values. In this example with [1, "Hey"] our array type is array<int | string>, which is invalid Rescript. But, if we convert those values to values first, then our type is array<value>, which is totally valid Rescript! Then for the 2nd function argument to array, which is normally converts each array element to a value, we just return the argument because it's already a value.

list​

let list: (list<'i>, 'i => value) => value

Turn a list into a JSON array.

list(list{1, 2, 3}, int)->encode(~indentLevel=0)         == "[1,2,3]"
list(list{true, false}, bool)->encode(~indentLevel=0)    == "[true,false]"
list(list{"a", "b"}, string)->encode(~indentLevel=0)     == "[\"a\",\"b\"]"

Objects​

object​

let object: array<(string, value)> => value

Create a JSON object.

let maria: value =
  object([
    ("name", "Maria"),
    ("age", 26),
  ])

encode(maria, 0) == "{\"name\":\"Maria\",\"age\":26}"

dict​

let dict: Js.Dict.t<value> => value

Turn a Js.Dict.t into a JSON object.

let maria: value =
  [
    ("name", "Maria"),
    ("age", 26),
  ]
  ->Js.Dict.fromArray

encode(maria, 0) == "{\"name\":\"Maria\",\"age\":26}"