A.2. Variables

Variables in ECMAScript are declared using the var keyword. Variable names must begin with a letter or an underscore followed by zero or more letters, numbers, and underscores. ECMAScript variables are case-sensitive.

ECMAScript supports weak typing. The programmer does not need to specify the type of a variable when declaring it; the interpreter automatically associates one of the five built-in ECMAScript types with the new variable based on the nature of the value assigned to it. These built-in types are shown in Table A-2.

var e = 2.71828;
var i = -1;

var b = true;

var s = "hello!";

var f = write;

var o = 
  new Employee("Smith",     
      "John", 35, 
      writeEmployeeRecord);

Depending on where a variable is declared, it can be a global or local variable. A global variable is visible from within all functions. A local variable is visible only within the function in which it is declared.