# RequestSubTextPartCallback Function

> Callback function for requesting a subtextpart.

- **Product:** DS Server
- **Section:** Reference
- **Kind:** Function
- **Path:** DS Server > Reference > JavaScript API > RequestSubTextPartCallback Function
- **365 words**
- **Web URL:** https://docs.textcontrol.com/ds-server/reference/javascript/requestsubtextpartcallback/
- **LLMs URL:** https://docs.textcontrol.com/ds-server/reference/javascript/requestsubtextpartcallback/llms.txt
- **LLMs-Full URL:** https://docs.textcontrol.com/ds-server/reference/javascript/requestsubtextpartcallback/llms-full.txt

---

### Description

Callback function for requesting a [subtextpart](https://docs.textcontrol.com/ds-server/reference/javascript/subtextpart/llms-full.txt).

### Syntax

```javascript
function(<SubTextPart> subTextPart)
```

### Examples

The following example demonstrates `RequestSubTextPartCallback` in a practical document-editing workflow. Callback function for requesting a subtextpart.

```javascript
function onTxError(error) {
    console.error("TX Text Control error:", error.msg);
    error.handled = true;
}

function requestSubTextPartCallback(subTextPart) {
    console.log("sub text part:", subTextPart);
}

TXTextControl.textParts.getMainText(function(mainText) {
    const subTextParts = mainText.subTextParts;
    subTextParts.getItem(function(subTextPart) {
        if (!subTextPart) {
            console.warn("No sub text part is available at the current input position.");
            return;
        }
    
        subTextPart.getOuterMostSubTextPart(requestSubTextPartCallback, onTxError);
    }, onTxError);
}, onTxError);
```

---

## Nearby

- **Previous:** [RequestStringsCallback Function](https://docs.textcontrol.com/ds-server/reference/javascript/requeststringscallback/llms-full.txt)
- **Next:** [RequestSubTextPartsCallback Function](https://docs.textcontrol.com/ds-server/reference/javascript/requestsubtextpartscallback/llms-full.txt)