Decision support statements

An if/else statement in JavaScript and other programming languages is a control statement that allows for decision-making in your code. This type of statement performs a test based on an expression, that you specify at the top of the statement. If the test returns a value of true then the statements associated with the if block will run. If the test returns a value of false then the execution skips to the first else if block. This pattern continues until a value of true is returned in the test or the execution reaches the else statement. The following code example shows how this statement works:

var layerName = 'streets'; 
if (layerName == 'aerial') { 
    alert("An aerial map"); 
} 
else if (layerName == "hybrid") { 
    alert("A hybrid map"); 
} 
else { 
    alert("A street map"); 
}