String, Number, Boolean, Array, Object, Null, Undefined.
JavaScript String
A string is a variable which stores a series of characters like "John Doe".
A string can be any text inside quotes. You can use simple or double quotes:
var carname="Volvo XC60";
var carname='Volvo XC60';
var carname='Volvo XC60';
You can use quotes inside a string as long as they don't match the quotes surrounding the string:
var answer="It's alright";
var answer="He is called 'Johnny'";
var answer='He is called "Johnny"';
var answer="He is called 'Johnny'";
var answer='He is called "Johnny"';
Or you can put quotes inside a string by using the \ escape character:
var answer='It\'s alright';
JavaScript Number
JavaScript has only one type of number.
Numbers can be with or without decimals:
var pi=3.14;
var x=34;
var x=34;
The maximum number of decimals is 17.
Extra large or extra small numbers can be written with scientific notation:
var y=123e5; // 12300000
var z=123e-5; // 0.00123
var z=123e-5; // 0.00123
JavaScript Boolean
Booleans can have only two values: true or false.
var x=true
var y=false
var y=false
JavaScript Array
The following code creates an Array object called myCars:
var cars=new Array();
cars[0]="Saab";
cars[1]="Volvo";
cars[2]="BMW";
cars[0]="Saab";
cars[1]="Volvo";
cars[2]="BMW";
or (condensed array):
var cars=new Array("Saab","Volvo","BMW");
or (literal array):
var cars=["Saab","Volvo","BMW"];
JavaScript Object
An object is delimited by curly braces. Inside the braces the object's properties are defined as name and value pairs (name : value). The properties are separated by commas:
var person={firstname:"John", lastname:"Doe", id:5566};
The object (person) in the example above has 3 properties: fistname, lastname, and id.
Spaces and line breaks are not important:
var person={
firstname : "John",
lastname : "Doe",
id : 5566
};
firstname : "John",
lastname : "Doe",
id : 5566
};
You can address the object properties in two ways:
name=person.lastname;name=person["lastname"];
Null or Undefined
Non-existing is the value of a variable with no value.
Variables can be emptied by setting the value to null;
cars=null;
person=null;
person=null;
Declaring Variable Types
When you declare a new variable, you can declare its type using the "new" keyword:
var carname=new String;
var x= new Number;
var y= new Boolean;
var cars= new Array;
var person= new Object;
var x= new Number;
var y= new Boolean;
var cars= new Array;
var person= new Object;
All variables in JavaScript are objects. When you declare a variable you create a new object. |
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