Function toTimestamp

toTimestamp(value?: string | Date | null): number | undefined
Converts a date or date string to a timestamp in milliseconds, returns undefined if invalid
Parameters
- Optionalvalue: string | Date | null
  The date or date string to convert
Returns number | undefined
the timestamp in milliseconds, or undefined if invalid
Author
David Hsing
Example
```
toTimestamp('2023-01-01');    // 1672531200000
toTimestamp('invalid');    // undefined
toTimestamp(new Date('2023-01-01'));    // 1672531200000
```