ee.String.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 argument is a function that is called when the server returns an answer, receiving either a success value or a failure error message.

• In the JavaScript example, evaluate is used to transfer a server-side ee.String to the client for use in a ui.Label.

• The Python client library does not have an evaluate method for ee.String objects; ee.String.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
String.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.String object fetched from a feature property.
var stringServer = ee.Feature(null, {lc: 'grassland'}).getString('lc');

// Use evaluate to transfer server-side string to client for use in ui.Label.
stringServer.evaluate(function(stringClient) {
  print('Client-side primitive data type', typeof stringClient);  // string
  print('Client-side string', stringClient);  // grassland
  print('Client-side string used in ui.Label',
        ui.Label('Land cover: ' + stringClient));  // Land cover: grassland
});

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.String objects.
# Use ee.String.getInfo() instead.