# String.index_of

## Function

Returns the position of the first occurrence of the specified fragment.

## Syntax

```bt
string.index_of(needle)
```

## Parameters

| Parameters | Type | Required | Default value | Description |
| ------ | ------ | ------ | ------ | ------ |
| needle | Any | No | '' | The fragment to be found will be converted into a string first when called. |

## Return value

| Type | Description |
| ------ | ------ |
| Int | Returns the starting byte position if found; returns -1 if not found. |

## Example

```bt
text = 'hello BT'
result = text.index_of('BT')

// Output: 6
print result
```

## Notes

- The return value comes from the Rust string lookup result, and the position is calculated as a UTF-8 byte offset.