# @onflow/types

> Utilities to transform javascript values into Cadence understandable values

Latest version **1.5.0** (published 2025-11-06) · Apache-2.0 license · 0 weekly downloads

## Install

```sh
npm install @onflow/types
pnpm add @onflow/types
yarn add @onflow/types
bun add @onflow/types
```

## Health

**Score 65/100 (B)** — status: stable.

Positive: has types; esm support; no vulnerabilities; high maintenance score; high quality score.

Warnings: low downloads.

## Facts

| | |
|---|---|
| Version | 1.5.0 |
| Published | 2025-11-06 |
| First published | 2020-04-17 |
| Weekly downloads | 0 |
| License | Apache-2.0 |
| TypeScript types | bundled |
| Module format | ESM + CommonJS |
| Dependencies | 2 |
| Unpacked size | 241.5 KB |
| Known vulnerabilities | 0 |
| Install scripts | no |
| GitHub stars | 333 |
| Author | Flow Foundation |
| Maintainers | han210, dapperj, dapper_labs, jeffreydoyle, harry.eth, turbolent_flow, chasefleming, gregsantos, gregorggg, jribbink, bthaile, nialexsan, sisyphussmiling, lmcmze |

## Links

- npm: https://www.npmjs.com/package/@onflow/types
- Repository: https://github.com/onflow/fcl-js
- Homepage: https://flow.com
- Issues: https://github.com/onflow/fcl-js/issues
- npm.io page: https://npm.io/package/@onflow/types

## Dependencies (2)

- [@babel/runtime](https://npm.io/package/@babel/runtime.md) ^7.25.7
- [@onflow/util-logger](https://npm.io/package/@onflow/util-logger.md) 1.3.4

## Recent versions

- 1.5.0 (latest) — 2025-11-06
- 1.4.1-alpha.0 (alpha) — 2024-10-22
- 1.3.0-event-streaming.1 (event-streaming) — 2023-11-29
- 1.2.0-typescript.0 (typescript) — 2023-11-01
- 1.4.2 — 2025-09-08
- 1.4.1 — 2024-11-27
- 1.4.0 — 2024-05-20
- 1.3.0 — 2024-03-26
- 1.3.0-alpha.3 — 2024-01-22
- 1.3.0-alpha.2 — 2023-12-07
- 1.3.0-alpha.1 — 2023-12-07
- 1.3.0-alpha.0 — 2023-12-04
- 1.3.0-event-streaming.0 — 2023-11-29
- 1.2.1 — 2023-11-09
- 1.2.0 — 2023-10-22
- … 21 more at https://npm.io/package/@onflow/types/versions

## README

---
title: Types
description: Translates JavaScript values into equivalent Cadence compatible values
---



## Status

- **Last Updated:** July 10 2020
- **Stable:** Yes
- **Risk of Breaking Change:** Medium

## Install

```bash
npm install --save @onflow/types
```

## Usage

### Transactions

```javascript
import * as sdk from "@onflow/sdk"
import * as t from "@onflow/types"

sdk.build([
  sdk.transaction`
    transaction(to: Address, amount: UFix64) {
      execute {
        let addr: Address = to
        let value: UFix64 = amount
      }
    }
  `,
  sdk.args([
    sdk.arg(to, t.Address),
    sdk.arg(amount, t.UFix64),
  ]),
])
```

### Scripts

```javascript
import * as sdk from "@onflow/sdk"
import * as t from "@onflow/types"

sdk.build([
  sdk.script`
    pub fun main(a: Int, b: Int): Int {
      return a + b
    }
  `,
  sdk.args([
    sdk.arg(1, t.Int),
    sdk.arg(2, t.Int),
  ]),
])
```

# Available Types

### UInt

```javascript
import * as t from "@onflow/types"

sdk.build([
  sdk.args([ sdk.arg(1, t.UInt) ])
])
```

### Int

```javascript
import * as t from "@onflow/types"

sdk.build([
  sdk.args([ sdk.arg(1, t.Int) ])
])
```

### UInt8

```javascript
import * as t from "@onflow/types"

sdk.build([
  sdk.args([ sdk.arg(8, t.UInt8) ])
])
```

### Int8

```javascript
import * as t from "@onflow/types"

sdk.build([
  sdk.args([ sdk.arg(8, t.Int8) ])
])
```

### UInt16

```javascript
import * as t from "@onflow/types"

sdk.build([
  sdk.args([ sdk.arg(16, t.UInt16) ])
])
```

### Int16

```javascript
import * as t from "@onflow/types"

sdk.build([
  sdk.args([ sdk.arg(16, t.Int16) ])
])
```

### UInt32

```javascript
import * as t from "@onflow/types"

sdk.build([
  sdk.args([ sdk.arg(32, t.UInt32) ])
])
```

### Int32

```javascript
import * as t from "@onflow/types"

sdk.build([
  sdk.args([ sdk.arg(32, t.Int32) ])
])
```

### UInt64

```javascript
import * as t from "@onflow/types"

sdk.build([
  sdk.args([ sdk.arg(64, t.UInt64) ])
])
```

### Int64

```javascript
import * as t from "@onflow/types"

sdk.build([
  sdk.args([ sdk.arg(64, t.Int64) ])
])
```

### UInt128

```javascript
import * as t from "@onflow/types"

sdk.build([
  sdk.args([ sdk.arg(128, t.UInt128) ])
])
```

### Int128

```javascript
import * as t from "@onflow/types"

sdk.build([
  sdk.args([ sdk.arg(128, t.Int128) ])
])
```

### UInt256

```javascript
import * as t from "@onflow/types"

sdk.build([
  sdk.args([ sdk.arg(256, t.UInt256) ])
])
```

### Int256

```javascript
import * as t from "@onflow/types"

sdk.build([
  sdk.args([ sdk.arg(256, t.Int256) ])
])
```

### Word8

```javascript
import * as t from "@onflow/types"

sdk.build([
  sdk.args([ sdk.arg(8, t.Word8) ])
])
```

### Word16

```javascript
import * as t from "@onflow/types"

sdk.build([
  sdk.args([ sdk.arg(16, t.Word16) ])
])
```

### Word32

```javascript
import * as t from "@onflow/types"

sdk.build([
  sdk.args([ sdk.arg(32, t.Word32) ])
])
```

### Word64

```javascript
import * as t from "@onflow/types"

sdk.build([
  sdk.args([ sdk.arg(64, t.Word64) ])
])
```

### Word128

```javascript
import * as t from "@onflow/types"

sdk.build([
  sdk.args([ sdk.arg(128, t.Word128) ])
])
```

### Word256

```javascript
import * as t from "@onflow/types"

sdk.build([
  sdk.args([ sdk.arg(256, t.Word256) ])
])
```

### UFix64

```javascript
import * as t from "@onflow/types"

sdk.build([
  sdk.args([ sdk.arg("64.123", t.UFix64) ])
])
```

### Fix64

```javascript
import * as t from "@onflow/types"

sdk.build([
  sdk.args([ sdk.arg("64.123", t.Fix64) ])
])
```

### UFix128

```javascript
import * as t from "@onflow/types"

sdk.build([
  sdk.args([ sdk.arg("128.123456789012345678901234", t.UFix128) ])
])
```

### Fix128

```javascript
import * as t from "@onflow/types"

sdk.build([
  sdk.args([ sdk.arg("128.123456789012345678901234", t.Fix128) ])
])
```

### String

```javascript
import * as t from "@onflow/types"

sdk.build([
  sdk.args([ sdk.arg("Flow", t.String) ])
])
```

### Character

```javascript
import * as t from "@onflow/types"

sdk.build([
  sdk.args([ sdk.arg("c", t.Character) ])
])
```

### Bool

```javascript
import * as t from "@onflow/types"

sdk.build([
  sdk.args([ sdk.arg(true, t.Bool) ])
])
```

### Address

```javascript
import * as t from "@onflow/types"

sdk.build([
  sdk.args([ sdk.arg("0xABC123DEF456", t.Address) ])
])
```



### Optional

```javascript
import * as t from "@onflow/types"

sdk.build([
  sdk.args([ sdk.arg("Flow", t.Optional(t.String)) ])
])

sdk.build([
  sdk.args([ sdk.arg(null, t.Optional(t.String)) ])
])
```


### Array

```javascript
import * as t from "@onflow/types"

sdk.build([
  sdk.args([ sdk.arg(["First", "Second"], t.Array(t.String)) ])
])

sdk.build([
  sdk.args([ sdk.arg(["First", 2], t.Array([t.String, t.Int])) ])
])
```

### Dictionary

```javascript
import * as t from "@onflow/types"

sdk.build([
  sdk.args([
    sdk.arg(
      [
        {key: 1, value: "one"},
        {key: 2, value: "two"},
      ],
      t.Dictionary({key: t.Int, value: t.String})
    )
  ])
])

sdk.build([
  sdk.args([
    sdk.arg(
      [
        {key: "a", value: "one"},
        {key: "b", value: "two"},
      ],
      t.Dictionary({key: t.String, value: t.String})
    )
  ])
])
```

### Path

```javascript
import * as t from "@onflow/types"

sdk.build([
  sdk.args([
    sdk.arg(
      {
        domain: "public"                // public | private | storage
        identifier: "flowTokenVault"
      },
      t.Path
    )
  ])
])
```

# Exist but not supported

The following, while technically possible, are impractical. We strongly recommend not using them as arguments for transactions or scripts.

### Void

```javascript
import * as t from "@onflow/types"

sdk.build([
  sdk.args([ sdk.arg(null, t.Void) ])
])
```

### Event

```javascript
import * as t from "@onflow/types"

sdk.build([
  sdk.args([
    sdk.arg(
      {
        fields: [{name: "wasTheCodeClean?", value: "absolutely"}],
      },
      t.Event("0xABC123DEF456.JeffWroteSomeJS", [{value: t.String}]),
    )
  ])
])
```


### Reference

```javascript
import * as t from "@onflow/types"

sdk.build([
  sdk.args([ sdk.arg({address: "0xABC123DEF456", type: "0xABC123DEF456.CryptoKitty"}, t.Reference) ])
])
```

### Struct

```javascript
import * as t from "@onflow/types"

sdk.build([
  sdk.args([
    sdk.arg(
      {
        fields: [{name: "CryptoKitty_name", value: "Lil' Jimmy The CryptoKitty"}],
      },
      t.Struct("0xABC123DEF456.CryptoKitty", [{value: t.String}])
    )
  ])
])
```

### Resource

```javascript
import * as t from "@onflow/types"

sdk.build([
  sdk.args([
    sdk.arg(
      {
        fields: [{name: "Jeffysaur_Name", value: "Mr Jeff The Dinosaur"}],
      }
      t.Resource("0x01.Jeffysaur", [{value: t.String}]),
    )
  ])
])
```

### InclusiveRange

```javascript
import * as t from "@onflow/types"

sdk.build([
  sdk.args([ sdk.arg({start: "1", end: "10", step: "1"}, t.InclusiveRange(t.Int)) ])
])
```

---
_Source: https://npm.io/package/@onflow/types · Machine-readable twin of the npm.io package page. Health data is recomputed on every publish._