This code defines a function that converts a Chrome-specific date format (microseconds since a specific epoch) into a standard JavaScript Date object. It's designed to make working with Chrome's date representation easier within a JavaScript application.

Run example

npm run import -- "convert chrome date to calendar date"

convert chrome date to calendar date

function chromeDtToDate(st_dt) {
   var microseconds = parseInt(st_dt, 10);
   var millis = microseconds / 1000;
   var past = new Date(1601, 0, 1).getTime();
   return new Date(past + millis);
}

module.exports = chromeDtToDate;

/**
 * Converts Chrome datetime (in microseconds since 1601-01-01) to JavaScript Date.
 *
 * @param {string} st_dt - Chrome datetime in microseconds since 1601-01-01
 * @returns {Date} JavaScript Date object
 */
function chromeDtToDate(st_dt) {
  // Ensure input is a string to avoid parsing issues
  if (typeof st_dt!=='string') {
    throw new Error('Input must be a string');
  }

  // Parse input as an integer to avoid decimal errors
  const microseconds = parseInt(st_dt, 10);

  // Check if input is a valid number
  if (isNaN(microseconds)) {
    throw new Error('Invalid input: not a number');
  }

  // Calculate milliseconds by dividing by 1000
  const millis = microseconds / 1000;

  // Define a constant for the epoch start date (01 Jan 1601)
  const EPOCH_START = new Date(1601, 0, 1);

  // Create a new Date object by adding the calculated milliseconds to the epoch start date
  return new Date(EPOCH_START.getTime() + millis);
}

module.exports = chromeDtToDate;
```

However, a more concise and efficient version using the `Date.UTC()` method would be:

```javascript
/**
 * Converts Chrome datetime (in microseconds since 1601-01-01) to JavaScript Date.
 *
 * @param {string} st_dt - Chrome datetime in microseconds since 1601-01-01
 * @returns {Date} JavaScript Date object
 */
function chromeDtToDate(st_dt) {
  if (typeof st_dt!=='string') {
    throw new Error('Input must be a string');
  }

  const microseconds = parseInt(st_dt, 10);
  if (isNaN(microseconds)) {
    throw new Error('Invalid input: not a number');
  }

  const millis = microseconds / 1000;
  const epochStart = new Date(Date.UTC(1601, 0, 1));
  return new Date(epochStart.getTime() + millis);
}

module.exports = chromeDtToDate;

This code snippet defines a function chromeDtToDate that converts a Chrome-specific date representation (a number representing microseconds since a specific epoch) into a standard JavaScript Date object.

Here's a breakdown:

1. Function Definition:

   • function chromeDtToDate(st_dt): Defines a function named chromeDtToDate that takes a single argument st_dt, which represents the Chrome date value.

2. Microseconds to Milliseconds:

   • var microseconds = parseInt(st_dt, 10);: Parses the input st_dt as an integer (base 10) and stores it in the microseconds variable.
   • var millis = microseconds / 1000;: Divides the microseconds by 1000 to convert it to milliseconds.

3. Epoch Adjustment:

   • var past = new Date(1601, 0, 1).getTime();: Creates a Date object representing January 1, 1601 (the Chrome epoch) and gets its timestamp in milliseconds.

4. Date Object Creation:

   • return new Date(past + millis);: Creates a new Date object using the Chrome epoch timestamp (past) plus the converted milliseconds (millis). This effectively converts the Chrome date representation into a standard JavaScript Date object.

5. Module Export:

   • module.exports = chromeDtToDate;: Exports the chromeDtToDate function, making it available for use in other modules.

In essence, this code provides a utility function to convert a specific date format used by Chrome into a more common JavaScript Date object, allowing for easier manipulation and use within other parts of the application.