---
title: abi.encodeFunctionData
description: "Builds smart contract calldata from a single function ABI fragment and arguments: the 4-byte selector plus ABI-encoded params, returned as hex without 0x."
keywords: ["encodefunctiondata", "utils", "calldata", "abi encode", "function selector", "tronweb"]
---
# abi.encodeFunctionData <TitleWithCodeLink2 link="abi.encodeFunctionData" />

> Added in **6.4.0**.

This method builds the **calldata** for a smart contract method: the 4-byte function
selector followed by the ABI-encoded parameters. It is the building block behind
contract calls, and is useful when you need the raw `data` field yourself (e.g. to pass
to `triggerSmartContract` / `triggerConstantContract`, or for an offline transaction).

For just the parameter encoding (without the selector), use
[abi.encodeParamsV2ByABI](./encodeParamsV2ByABI.md).

### Usage
```js
tronWeb.utils.abi.encodeFunctionData(funcABI, args);
```

### Parameters
| Parameter | Description | Data Type |
| --------- | ----------- | --------- |
| funcABI | A **single** function ABI fragment — `{ type: 'function', name, inputs, outputs? }` — **not** the whole ABI array. | object (`FunctionFragment`) |
| args | Optional. The function arguments, in ABI order. Defaults to `[]`. | array |

**Notes**

- Pass **one** function fragment, not the whole contract ABI array — extract the entry for the method (e.g. `abi.find((f) => f.name === 'transfer')`).
- The returned hex string has **no** `0x` prefix.
- `args.length` must equal `funcABI.inputs.length`, otherwise it throws
  `Invalid arguments provided: expected N arguments, got M`.
- A non-`function` fragment (or one without a `name`) throws
  `Invalid function ABI fragment provided: only "function" type fragments with a name are supported`.
- TRON's `trcToken` is kept in the **selector** signature (TVM convention) but encoded as
  `uint256` in the parameters. Base58 addresses inside `args` are converted to hex
  automatically.

### Returns
hex string - The calldata: `selector (8 hex chars)` + ABI-encoded parameters, **without** a `0x` prefix.

### Example
```js
// transfer(address,uint256)
const funcABI = {
  name: 'transfer',
  type: 'function',
  inputs: [
    { name: 'to', type: 'address' },
    { name: 'amount', type: 'uint256' },
  ],
  outputs: [],
};
const data = tronWeb.utils.abi.encodeFunctionData(funcABI, ['TMVQGm1qAQYVdetCeGRRkTWYYrLXuHK2HC', 100]);
// output-start
'a9059cbb0000000000000000000000007e5f4552091a69125d5dfcb7b8c2659029395bdf0000000000000000000000000000000000000000000000000000000000000064'
// output-end

// a function without parameters returns only the selector
tronWeb.utils.abi.encodeFunctionData({ name: 'totalSupply', type: 'function', inputs: [], outputs: [] });
// output-start
'18160ddd'
// output-end

// trcToken stays in the selector, value is encoded as uint256
tronWeb.utils.abi.encodeFunctionData(
  { name: 'transfer', type: 'function', inputs: [{ name: 'id', type: 'trcToken' }], outputs: [] },
  [1000100]
);
// output-start
'e7bf839c00000000000000000000000000000000000000000000000000000000000f42a4'
// output-end
```