JavaScript Basics

Array
Boolean
Date
Math
Number
String
RegExp

Window
Navigator
Screen
History
Location

Document
Events
Elements

1.
var myCars=new Array(); // regular array (add an optional integer
myCars[0]="Saab"; // argument to control array's size)
myCars[1]="Volvo";
myCars[2]="BMW";

2.
var myCars=new Array("Saab","Volvo","BMW"); // condensed array

3.
var myCars=["Saab","Volvo","BMW"]; // literal array

They mean different things. If you use var the variable is declared within the scope you are in (e.g. of the function). If you don't use var, the variable is automatically global, and attached to the global object (window, if you are doing it in the browser).

if (condition1)
{
code to be executed if condition1 is true
}
else if (condition2)
{
code to be executed if condition2 is true
}
else
{
code to be executed if condition1 and condition2 are not true
}

switch(n)
{
case 1:
execute code block 1
break;
case 2:
execute code block 2
break;
default:
code to be executed if n is different from case 1 and 2
}

function functionname(var1,var2,...,varX)
{
some code
}

for (var=startvalue;var<=endvalue;var=var+increment)
{
code to be executed
}

while (var<=endvalue)
{
code to be executed
}

var i=0;
for (i=0;i<=10;i++)
{
if (i==3)
{
break;
}
document.write("The number is " + i);
document.write("<br />");
}

for (variable in object)
{
code to be executed
}

try
{
//Run some code here
}
catch(err)
{
//Handle errors here
}

throw(exception)

The exception can be a string, integer, Boolean or an object.

var txt="We are the so-called \"Vikings\" from the north.";