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  • JS is a cross-platform object oriented scripting language.
  • Is designed for easy embedding in other products and applications, such as web browsers.
  • Core JS consists of a set of objects e.g. Array, Date and Math and language elements such as operators and control structures.
  • Client-side JavaScript extends the core language by supplying objects to control a browser and its Document Object Model (DOM). e.g, client-side extensions allow an application to place elements on an HTML form and respond to user events such as mouse clicks, form input, and page navigation.
  • JS as opposed to say, Java, is loosely typed.

Values, Variables and Literals

  • JS is dynamically typed. So, the following is possible:
var ans = 42;

ans = "Forty two";
  • Variable scope : only two, local and global. No block scope!
  • Local variables belong to the defined function.
  • Global variables belong to the global object. In web pages, the global object is window.
  • An object literal is a list of zero or more pairs of property names and associated values of an object, enclosed in curly braces ({}).
var cc = "1300cc";

function carTypes(name) {
 if(name == "Vista") {
   return "Tata Indica Vista";

var car = {myCar : "Vista", getCar : carTypes("Vista"), engine : cc};