npm package: @onflow/types
Description: Utilities to transform javascript values into Cadence understandable values
Author: Flow Foundation
Latest version: 1.5.0

---
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)) ])
])
```