Json overview

Added in v2.10.0

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Table of contents

• utils
  • Json (type alias)
  • JsonArray (interface)
  • JsonRecord (interface)
  • parse
  • stringify

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utils

Json (type alias)

Signature

export type Json = boolean | number | string | null | JsonArray | JsonRecord

Added in v2.10.0

JsonArray (interface)

Signature

export interface JsonArray extends ReadonlyArray<Json> {}

Added in v2.10.0

JsonRecord (interface)

Signature

export interface JsonRecord {
  readonly [key: string]: Json
}

Added in v2.10.0

parse

Converts a JavaScript Object Notation (JSON) string into a Json type.

Signature

export declare const parse: (s: string) => Either<unknown, Json>

Example

import * as J from 'fp-ts/Json'
import * as E from 'fp-ts/Either'
import { pipe } from 'fp-ts/function'

assert.deepStrictEqual(pipe('{"a":1}', J.parse), E.right({ a: 1 }))
assert.deepStrictEqual(
  pipe('{"a":}', J.parse),
  E.left(new SyntaxError(`Unexpected token '}', "{"a":}" is not valid JSON`))
)

Added in v2.10.0

stringify

Converts a JavaScript value to a JavaScript Object Notation (JSON) string.

Signature

export declare const stringify: <A>(a: A) => Either<unknown, string>

Example

import * as E from 'fp-ts/Either'
import * as J from 'fp-ts/Json'
import { pipe } from 'fp-ts/function'

assert.deepStrictEqual(J.stringify({ a: 1 }), E.right('{"a":1}'))
const circular: any = { ref: null }
circular.ref = circular
assert.deepStrictEqual(
  pipe(
    J.stringify(circular),
    E.mapLeft((e) => e instanceof Error && e.message.includes('Converting circular structure to JSON'))
  ),
  E.left(true)
)

Added in v2.10.0