Introduction to JavaScript | Remote Sensing Course

Let's start our programming journey. JavaScript is the language of the Earth Engine Code Editor. We will use it to describe data, call API functions, and visualize results. You do not need to be a JavaScript specialist; we need just enough syntax to read, tweak, and write short scripts.

Learning objectives

Describe what JavaScript is and why the course starts with it.
Recognize basic syntax for variables, strings, numbers, and comments.
Run a short script in the Code Editor to print and map something.
Know where to go next for lists, objects, functions, and client vs server.

Why it matters

The Code Editor uses JavaScript for instant feedback, sharing, and UI tools. Learning a small set of patterns lets you focus on remote sensing questions instead of setup.

Google Earth Engine Code Editor with script, console, and map — Write code, view docs, inspect the console, and see the map in one place.

Quick win: first script

Paste into the Code Editor and click Run:

// Hello Earth Engine
var pt = ee.Geometry.Point([-82.3248, 29.6516]); // Gainesville, FL
Map.centerObject(pt, 9);
Map.addLayer(pt, {color: 'orange'}, 'My point');
print('A friendly hello from Earth Engine');

What we should see

An orange point on the map centered on Florida and a console message greeting you.

Key vocabulary

Variable: A named container for data (for example, var city = 'Gainesville';).
String: Text data inside quotes (single or double).
Number: Numeric data without quotes (integers or decimals).
Comment: Notes for humans, ignored by the computer (// single line or /* block */).

Basic syntax patterns to remember

Declare once, reuse often: var roi = ... then pass roi to filters and reducers.
Semicolons: Optional in JavaScript, but using them keeps scripts tidy.
Case-sensitive: Map is different from map; ndvi is different from NDVI.
Use print() to inspect: It sends requests to the server and returns results in the console.

Try it: small tweaks, fast feedback

Change the point coordinates to your hometown and re-run.

Swap the color to 'green' and zoom to 12.

Add a label by printing a sentence that includes your city name.

Common mistakes

Forgetting quotes around text: var city = Gainesville; will error.
Using curly quotes from word processors instead of plain quotes.
Mixing client-only objects with server objects (covered in Client vs Server).

Quick self-check

What happens if you remove the quotes around a string-
How do you add a comment in JavaScript-
Why is JavaScript the default language in the Earth Engine Code Editor-

Where to go next

Variables: storing and naming data
Lists and Objects: organizing data
Functions: reusable logic
Client vs Server: the most important Earth Engine distinction

Going Deeper: EEFA Book

This module gives us the foundation. To explore further, see Chapter F1.0 (JavaScript and the Earth Engine API) in the Cloud-Based Remote Sensing with Google Earth Engine (EEFA Book).