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[`FileManager`](FileManager) › [`processFrontMatter`](FileManager/processFrontMatter)
## FileManager.processFrontMatter() method
Atomically read, modify, and save the frontmatter of a note. The frontmatter is passed in as a JS object, and should be mutated directly to achieve the desired result.
Remember to handle errors thrown by this method.
**Signature:**
```typescript
processFrontMatter(file: TFile, fn: (frontmatter: any) => void, options?: DataWriteOptions): Promise<void>;
```
## Parameters
| Parameter | Type | Description |
| --- | --- | --- |
| <code>file</code> | [`TFile`](TFile) | the file to be modified. Must be a markdown file. |
| <code>fn</code> | <code>(frontmatter: any) => void</code> | a callback function which mutates the frontmatter object synchronously. |
| <code>options</code> | [`DataWriteOptions`](DataWriteOptions) | _(Optional)_ write options. |
**Returns:**
`Promise``<void>`
## Exceptions
YAMLParseError if the YAML parsing fails
any errors that your callback function throws