Objects

Objects store labeled data as key-value pairs. They make your code more readable than lists when you care about names instead of positions.

Learning objectives

  • Create objects with curly braces and key-value pairs.
  • Access values by key using .get().
  • Use camelCase naming to keep code clear.
  • Understand when to choose objects over lists.

Why it matters

Objects let you bundle metadata (location, dates, band lists) together in a self-documenting way. Earth Engine also returns many results as objects, so reading them is essential.

Quick win: make and inspect an object

var cityData = {
  name: 'Gainesville',
  coordinates: [-82.3248, 29.6516],
  population: 140398
};
print('City data', cityData);

What you should see

A console entry labeled "Dictionary" with keys name, coordinates, and population.

Console output showing object key-value pairs
Objects show keys so you can access values by name.

Accessing values

Use .get() with the key name:

var cityName = cityData.get('name');
var coords = cityData.get('coordinates');
print('City name:', cityName);
print('Coordinates:', coords);

Key concepts

  • Syntax: { key: value, anotherKey: value }
  • Keys are strings: You can quote them or not; be consistent.
  • Comma separated: Each key-value pair ends with a comma except the last.
  • Nested values: Values can be strings, numbers, lists, or other objects.

Try it: build your own

Create an object for a study site with keys name, lat, lon, and sensor. Print it.

Add a bands key that stores a list of band names.

Make another object and compare keys to see how objects stay readable.

Common mistakes

  • Leaving out commas between pairs.
  • Forgetting quotes around string values.
  • Mixing client objects with Earth Engine objects: use ee.Dictionary when you need an object on the server.

Quick self-check

  1. What is the key for retrieving the population in the example above-
  2. When would you prefer an object over a list-
  3. How do you access a value stored under a key-

Next steps