Intro to Javascript

Introduction to Javascript

(My Understanding from different reads)

Types

It all starts with Data Types and following are them to start with.

Declarations:

    var a;          // Declaration
    a = 0;          // a has a value.
    // TYPES
    a = 2;          // Numbers
    a = 0.01;       // Both Integers and Real fall under Numbers
    a = "js";       // String Declarations using Single Quote
    a = 'js';       // String Declarations using Double Quote.
    a = true;       // Boolean
    a = false;      // alternate value of Boolean
    a = null;       // null is a special value which means a null -- will talk more
    a = undefined;  // undefined is similar to null -- will talk more.

Objects & Arrays

Hmm.... Objects and Arrays integral part of each and every programming language.

Object:

An object is a collection of name/value pairs, or a string to value map

Array:

Array is a numerically indexed lists of values

    //OBJECTS

    var book = {
        title : "JS",
        taf : true
    };

    //Access

    book.title              // Access with  .  or [ ]
    book["taf"]
    book.name = "JSBOOK";   // Add properties
    book.contents = {} ;    // empty object

    //ARRAYS can be accessed only with indexes in square brackets.

    var primes = [2,3,4,5]
    primes[0]
    primes.length
    primes[primes.length - 1]

Arrays and Objects can hold other objects and arrays

    var coordinates = [
        {x:0,y:0},
        {x:1,y:1}
    ];

    var data = {
        d1: [[1,2],[3,4]],
        d2: [[2,3],[4,5]]
    };

Expressions & Operators

Initializer Expression

Syntax for listing array elements within Square braces or mapping Object Property names to property values inside curly braces.

Expression:

computes a value, but doesnot do anything, doesnot change the state of program in anyway.

Statements

Statement:

Do not have a value but they alter the state of program.

Functions

A function is a named and parametrized block of JavaScript code that you define once, and can then invoke over and over again. When we combine functions with objects, we get methods: Client-side JavaScript does not exhibit the nonlinear cross-reference problem nearly to the extent that the core language does, and it is possible to learn how to use JavaScript in web browsers in a fairly linear sequence. There are two exceptions to the general rule that JavaScript interprets line breaks as semicolons when it cannot parse the second line as a continuation of the statement on the first line. The first exception involves the return, break, and continue statements The second exception involves the ++ and −− operators