JSON

Parse

Bind to JavaScript's JSON.parse and type the return value as the type you're expecting:

// declare the shape of the json you're binding to
type data = {names: array<string>}

// bind to JS' JSON.parse
@scope("JSON") @val
external parseIntoMyData: string => data = "parse"

let result = parseIntoMyData(`{"names": ["Luke", "Christine"]}`)
let name1 = result.names[0]

Where data can be any type you assume the JSON is. As you can see, this compiles to a straightforward JSON.parse call. As with regular JS, this is convenient, but has no guarantee that e.g. the data is correctly shaped, or even syntactically valid. Slightly dangerous.

Stringify

Use JSON.stringify:

Console.log(JSON.stringify(["Amy", "Joe"]))

Import a JSON file

Use the @module attribute to import JSON files directly.

@module external studentNames: JSON.t = "./students.json"
Console.log(studentNames)

Advanced

Thanks to untagged variants, JSON can be encoded and decoded idiomatically. Check it out on the variants page.