ee.Date.evaluate

AI-generated Key Takeaways

• The evaluate method asynchronously retrieves the value of an object from the server and passes it to a provided callback function.

• The callback function is executed when the server returns an answer, receiving either the successful result or a failure message.

• In JavaScript, the evaluate method transfers a server-side ee.Date object to the client as an object containing "type" and "value" keys, where "value" is milliseconds since the Unix epoch.

• The Python client library does not have an evaluate method for asynchronous evaluation of ee.Date objects; ee.Date.getInfo() should be used instead.

Asynchronously retrieves the value of this object from the server and passes it to the provided callback function.

Usage	Returns
Date.evaluate(callback)

Argument	Type	Details
this: computedobject	ComputedObject	The ComputedObject instance.
callback	Function	A function of the form function(success, failure), called when the server returns an answer. If the request succeeded, the success argument contains the evaluated result. If the request failed, the failure argument will contains an error message.

Examples

Code Editor (JavaScript)

/**
 * WARNING: this function transfers data from Earth Engine servers to the
 * client. Doing so can negatively affect request processing and client
 * performance. Server-side options should be used whenever possible.
 * Learn more about the distinction between server and client:
 * https://developers.google.com/earth-engine/guides/client_server
 */

// A server-side ee.Date object.
var dateServer = ee.Date('2021-4-30');

// Use evaluate to transfer server-side date to the client. The result is
// an object with keys "type" and "value" where "value" is milliseconds since
// Unix epoch.
dateServer.evaluate(function(dateClient) {
  print('Client-side date is an object', typeof dateClient);
  print('Object keys include "type" and "value"', Object.keys(dateClient));
  print('"value" is milliseconds since Unix epoch', dateClient.value);
  print('Client-side date in JS Date constructor', new Date(dateClient.value));
});

Python setup

See the Python Environment page for information on the Python API and using geemap for interactive development.

import ee
import geemap.core as geemap

Colab (Python)

# The Earth Engine Python client library does not have an evaluate method for
# asynchronous evaluation of ee.Date objects.
# Use ee.Date.getInfo() instead.