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ethereum-qr-code

★ 83 Open GitHub ↗

Advanced QR code generator for Ethereum payments including token transfers

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# Ethereum Address QR Code Generator

This plugin provides a convenient way to generate an [ethereum address link out of the provided parameters based on EIP67](https://github.com/ethereum/EIPs/issues/67).

The plugin generates the string based on the provided parameters and translates it into a QR code using the following [qrcode plugin](https://www.npmjs.com/package/qrcode).

Demo: [https://jibrelnetwork.github.io/ethereum-qr-code/](https://jibrelnetwork.github.io/ethereum-qr-code/)

[![Build Status](https://travis-ci.org/jibrelnetwork/ethereum-qr-code.svg?branch=master)](https://travis-ci.org/jibrelnetwork/ethereum-qr-code) ![DEPENDENCIES status](https://david-dm.org/jibrelnetwork/ethereum-qr-code.svg)

## Getting started

1. Install from NPM: `npm install ethereum-qr-code --save`
 2. Use in your code

```javascript
import EthereumQRPlugin from 'ethereum-qr-code'

// later in code
const qr = new EthereumQRPlugin()

const qrCode = qr.toCanvas({
  to: '0xsomeaddress',
  gas: 21000,
}, {
  selector: '#my-qr-code',
})
```

## Usage

### API

**`.toAddressString(config)`**

An encoder to translate your data into a string. Use if you want to generate a string.

Example:
```javascript
qr.toAddressString({
  to: '0x7cB57B5A97eAbe94205C07890BE4c1aD31E486A8',
  value: 100,
}) //> ethereum:0x7cB57B5A97eAbe94205C07890BE4c1aD31E486A8[?gas=21000][?value=100]

qr.toAddressString({
  to: '0x7cB57B5A97eAbe94205C07890BE4c1aD31E486A8',
  value: 10,
  gas: 42000,
}) //> ethereum:0x7cB57B5A97eAbe94205C07890BE4c1aD31E486A8[?gas=42000][?value=10]
```

**`.toCanvas(config, options)`**

Generates the canvas tag with the QR code. In this case the `selector` field becomes available.
Returns a Promise object that is resolved when the code is successfully generated.

Example:
```javascript
const qrCode = qr.toCanvas({
  to,
  gas,
}, {
  selector: '#my-qr-code',
})

qrCode.then((code) => {
  console.log('Your QR is generated!')
  console.log(code.value)
})
```

**`.toDataUrl(config, options)`**

A more flexible method that returns a QR in a dataUrl.
This method returns a Promise that is resolved when the code is successfully generated.

Example:
```javascript
const qrCode = qr.toDataUrl({
  to,
  gas,
  amount,
})

qrCode.then((qrCodeDataUri) => {
  console.log('Your QR id generated:', code.value) //> 'data:image/png;base64,iVBORw0KGgoA....'
})
```

**`.readStringToJSON(string)`**

A method to convert the EIP67 string back to the JSON object.

Example:
```javascript
const paymentParams = qr.readStringToJSON(
  'ethereum:0x7cB57B5A97eAbe94205C07890BE4c1aD31E486A8[?gas=4200][?value=150]',
)

console.log(paymentParams) //>
/*
{
  gas: '4200',
  value: '150',
  to: '0x7cB57B5A97eAbe94205C07890BE4c1aD31E486A8',
}
*/
```

## URI schemes

This QR code generator supports URI across three different use-cases:
1. Sending ETH
2. Invoking function of a contract
3. Sending `ERC20` tokens

We cover these 3 different cases using a parameter called 'mode'. The details are outlined below.

### 1. Sending ETH

URI scheme used to send ETH between accounts conforms early `EIP67` proposals and Bitcoin scheme.
This is built to be backward compatible.

`ethereum:<address>[?from=<sender_address>][?value=<ethamount>][?gas=<suggestedGas>]`

Parameters:

1. `to` | String | **required** - The address of the recipient account

2. `from` | String | optional - Address of the tx sender. Defaults to current active account of the sender app

3. `value` | Number | optional - Amount of ETH to send. Measured in `wei`. Defaults to 0.

4. `gas` | Number | optional - Recommended amount of gas. Defaults to 21000.

5. `chainId` | Number | optional - Contains id of a selected blockchain to which transaction should be limited [see EIP155 for details](https://github.com/ethereum/EIPs/blob/master/EIPS/eip-155.md).

These are the only parameters needed for this use-case.

For the other use-cases, the `mode` field allows for defining the structure of the resulting JSON. The URI scheme to invoke the contract's function uses JSON to encode the parameters specified.

Possible inputs for the `mode` field: 
- `contract_function`
- `erc20__transfer`
- `erc20__approve`
- `erc20__transferFrom`

These are explored in more detail below.

### 2. Invoke function of a contract

That mode is utilized by specifying `"mode: "contract_function"`.

Example of the `transfer` method using an `ERC20` token:

```json
{
  "to": "0xcontractaddress",
  "from": "0xsenderaddress",
  "value": 0,
  "gas": 100000,
  "mode": "contract_function",
  "functionSignature": {
    "name": "transfer",
    "payable": false,
    "args": [
      {
        "name": "to",
        "type": "address"
      },
      {
        "name": "value",
        "type": "uint"
      }
    ]
  },
  "argsDefaults": [
    {
      "name": "to",
      "value": "0xtokensrecipient"
    },
    {
      "name": "value",
      "value": 1000000000000000000
    }
  ]
}
```

Parameters:

1. `to` | String | **required** - Recipient address

2. `from` | String | optional - Sender address. Defaults to current active user account

3. `value` | Number | optional - Amount of ETH to send. Measured in `wei`. Defaults to 0.

4. `gas` | Number | optional - Recommended amount of gas. Defaults to 21000.

5. `chainId` | Number | optional - Contains id of a selected blockchain to which transaction should be limited [see EIP155 for details](https://github.com/ethereum/EIPs/blob/master/EIPS/eip-155.md).

6. `mode` | String | **required** - Mode of invocation. Expected value: `contract_function`

7. `functionSignature` | Object | **required** - Object that defines signature of invoked function. It is used only if `"mode" == "function"`

1. `name` | String | **required** - Name of the invoked function

2. `payable` | Boolean | **required** - Defines whether function is able to receive ETH or not. (`value` should be zero if `false`)

3. `args` | Array | **optional** - Contains list of function`s arguments. If this parameter is present - it must contain at least one element. If this parameter is not present - we assume that function do not have arguments.

1. `type` | String | **required** - Type of the argument: `uint`, `uint8`, `int32`, `address`, `bool` and so on.

2. `name` | String | **required** - Name of the argument. Used to generate GUI for the transaction.
        In fact, argument of Solidity function can be unnamed - this is OK if you develop a smart contract.
        But QR codes are used to pass tx details between different wallets and GUI must be nice.
        Therefore unnamed input fields in GUI are not possible. Therefore this parameter is required.

8. `argsDefaults` | Array | optional - Array with default values for function arguments. If this parameter is present - it must contain at least one element. We do not require to provide defaults of all args.

1. `name` | String | **required** - Name of the argument. Should be equal to the name of one of arguments from `functionSignature`

2. `value` | Any | **required** - Default value for the function argument

### 3. Template for `ERC20` tokens

The 3 extra subtypes were added since ERC20 tokens are very popular.

To make it easier to send tokens between accounts we predefine function signatures for the methods from ERC20 specification:

1. `"mode": "erc20__transfer"` will result in `function transfer(address to, uint value) returns (bool success)`
  2. `"mode": "erc20__approve"` => `function approve(address spender, uint value) returns (bool success)`
  3. `"mode": "erc20__transferFrom"` => `function transferFrom(address from, address to, uint value) returns (bool success)`

Example for `transfer` method:

```json
{
  "to": "0xcontractaddress",
  "from": "0xsenderaddress",
  "gas": 100000,
  "mode": "erc20__transfer",
  "argsDefaults": [
    {
      "name": "to",
      "value": "0xtokensrecipient"
    }
  ]
}
```

Functionally, this is similar to the previous example.

Parameters:

1. `to` | String | **required** - Recipient address

2. `from` | String | optional - Sender address. Defaults to current active account of the sender user

3. `gas` | Number | optional - Recommended amount of gas. Defaults to 21000.

4. `mode` | String | **required** - Mode of invocation. Expected value: `erc20__transfer`, `erc20__approve`, `erc20__transferFrom`

5. `chainId` | Number | optional - Contains id of a selected blockchain to which transaction should be limited [see EIP155 for details](https://github.com/ethereum/EIPs/blob/master/EIPS/eip-155.md).

6. `argsDefaults` | Array | optional - Array with default values for function arguments.

1. `name` | String | **required** - Name of the argument. Should be equal to the name of one of arguments from `functionSignature`

2. `value` | Any | **required** - Default value for the function argument

### Options argument - parameters of QR code generation

Optional parameters are passed via configuration object as a second parameter to `toDataUrl` and `toCanvas` methods. It has following fields:

1. `selector` | String | optional

If you want the plugin to generate the canvas tag and place the QR code into your page DOM, you need to provide the DOM element selector.

2. `options` | Object | optional

Allows to [override extra options](https://www.npmjs.com/package/qrcode#options-9) of the used qrcore plugin. Such as color, margin and scale. Use `option.scale` with caution. The plugin selects a default value based on the length of the data. Manually setting may result in an error.

3. `size` | String | optional

## Contact us

Or follow us on Twitter: [@JibrelNetwork](https://twitter.com/JibrelNetwork).

If you have a proposal, feature request, or are having trouble running the plugin,  please [submit an issue](https://github.com/jibrelnetwork/ethereum-qr-code/issues).

## License

[MIT](LICENSE.md)

ethereum-qr-code

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