Tutorial 1 & 2

Getting access

• Create (or verify) an email account associated with Google. e.g. abcdef\@gmail.com.

• Register for a GEE account at https://earthengine.google.com/signup/.

The GEE Interface (Code Editor)

Figure 1. Image of Code Editor highlighting components of layout.

Programming in JavaScript

• Every command line ends with a semi-colon (;)

• " and ' can be used interchangeably

• Use comments to make your code readable

  Comments start with // and any text in a line after the // is a comment

  Multi-line comments can start with /* and end with */

  or use Control and /

• Use the keyword var to create a variable e.g.

  var my_grade = 100;
  

• Parentheses are used to pass parameters to functions. e.g.

  print("This string will print in the Console tab.");
  

• String objects (i.e. text) start and end with a single quote e.g.

  var opinion = "GEE is awesome";
  

• Square brackets are used to specify items in a list.

  var my_list = ["eggplant", "apple", "wheat"];
  

• The zero index is the first item in the list e.g.

  print(my_list[0]);
  

• Square brackets can be used to access dictionary items by key e.g.

  print(my_dict["color"]);
  

• Or you can use the dot notation to get the same result.

  print(my_dict.color);
  

• Curly brackets (or braces) are used to define dictionaries (key:value pairs).

  var my_dict = {"food":"bread", "color":"red", "number":42};
  

• For mathematical operations, you can use the built-in mathematical functions or you can use the mathematical symbols directly:

  //build in function
  print(3.subtract(2)); 
      
  //mathematical symbols
  print(3-2);
      
  //making it more readable
  print("Subtracting two from three equals",3-2);
  

• Functions that combine commonly reused steps improve efficiency and make code easier to read. The my_hello_function below takes input from the user, adds some text and prints the result to the Console tab. The add_function takes an input value, adds 3, and then returns the results with an appropriate text description.

  var my_hello_function = function(string) { return "Hello " + string + "!"; }
  print(my_hello_function("world"));  //would print Hello world! in the Console tab
      
  var add_function = function(a) { return a+3; }; 
  var a = 1;
  print(a + " plus 3 is " + add_function(a));  //would print 1 plus 3 is 4 in the Console tab