# Export Transformer

With the **export** transformer, you can export almost anything out of Datasaur.\
\
Your new export transformer will have this template:

{% code title="" %}

```
/**
 * This function should be written as this template and return string.
 */
(document: Exportable): string => {
  /// Implement export function here
  return document.cells.map((cell) => cell.content).join('\n');
};
```

{% endcode %}

## Sample case

This example shows how to export a span labeling in a format compatible with Google AutoMl. The file transformer script is shown below, written in TypeScript:

```
function getCellMap(cells: Cell[]) {
  const cellMap = new Map<number, Cell>();
  cells.forEach(cell => {
    cellMap.set(cell.line, cell);
  })
  return cellMap;
}

function getLabelSetMap(labelSets: LabelSet[]) {
  const labelSetMap = new Map<string, LabelItem>();
  labelSets.forEach(labelSet => {
    labelSet.labelItems.forEach(labelItem => {
      labelSetMap.set(labelItem.id, labelItem);
    })
  });
  return labelSetMap;
}

function convertOffset(label: SimpleLabel, cell: Cell) {
  const offset = { "end_offset": 0, "start_offset": 0 };

  const startTokenIndex = label.startTokenIndex;
  const endTokenIndex = label.endTokenIndex;
  const startCharIndex = label.startCharIndex;
  const endCharIndex = label.endCharIndex;

  let offsetCounter = 0;
  for (let i = 0; i <= endTokenIndex; i++) {
    if (i == startTokenIndex) {
      offset.start_offset = offsetCounter + startCharIndex;
    }
    if (i == endTokenIndex) {
      offset.end_offset = offsetCounter + endCharIndex + 1;
      break
    }
    offsetCounter = offsetCounter + cell.tokens[i].length + 1;
  }
  return offset;
}

function stringifyWithSpaces(obj) {
	let result = JSON.stringify(obj, null, 1); // stringify, with line-breaks and indents
	result = result.replace(/^ +/gm, " "); // remove all but the first space for each line
	result = result.replace(/\n/g, ""); // remove line-breaks
	result = result.replace(/{ /g, "{").replace(/ }/g, "}"); // remove spaces between object-braces and first/last props
	result = result.replace(/\[ /g, "[").replace(/ \]/g, "]"); // remove spaces between array-brackets and first/last items
	return result;
}

/**
 * This function should be written as this template and return string.
 */
(document: Exportable): string => {
  /// Implement export function here
  const cellMap = getCellMap(document.cells);
  const labelSetMap = getLabelSetMap(document.labelSets);
  const examplesMap = new Map<number, Object>();

  document.labels.forEach(label => {
    const labelItem = labelSetMap.get(label.labelSetItemId);
    const cell = cellMap.get(label.startCellLine);
    const offset = convertOffset(label, cell);

    const annotation = { "text_extraction": {"text_segment": offset}, "display_name": labelItem.labelName };
    if (examplesMap.has(label.startCellLine)) {
      const example = examplesMap.get(label.startCellLine);
      example["annotations"].push(annotation);
      examplesMap.set(label.startCellLine, example);
    } else {
      const example = {
        "annotations": [annotation],
        "text_snippet": {"content": cell.tokens.join(' ')}
      };
      examplesMap.set(label.startCellLine, example);
    }
  });

  let output = [];
  examplesMap.forEach((value) => {
    output.push(stringifyWithSpaces(value));
  })
  return output.join('\n');
};
```

Follow these steps to upload and export using a custom export transformer:

1. Go to the **File transformers** page.
2. Click **Create file transformer.**
3. Enter a name, select **Export** as the purpose, then click **Create.**
4. Paste the file transformer script to the editor. You can also upload it.
5. Go to **Projects** page and open project you want to export.
6. Click **File** > **Export file**.
7. In the **Format** field, select **Custom Format (via File Transformer)**.
8. In the **Export as** field, add the `.jsonl` extension at the end of the file name.
9. In the **File transformer** field, select the file transformer you just created.

If you have any questions, please reach out to <support@datasaur.ai>.


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