Javascript

Javascript Output :

We have following ways through that we can display the output from javascript

1. document.getElementById(“demo”).innerHTML = 1+0; property of innerHTML of HTML to display the data..
2. document.write(“Pavan”); will be using for testing
3. <button type=”button” onclick=”document.write(‘Pavan’)”> it will delete all the html and show the output
4. window.alert(“Pavan”); //to show data in alert
5. console.log(“Pavan”); //Debuging purpose

Instructions:

Programming is nothing but the instrcution given by us to machine.
insruction are in the form of statements
javascript is nothing but list of statements eecuted from top to bottom

Statements contains: values,expressions,operators,comments and keywords.

Semicolon is used to indentify the end of statement.
we can break the line after operator.

 

Keywords:

1. break
2. continue
3. debugger
4. do..while
5. for
6. function
7. if..else
8. return
9. switch
10. try..catch
11. var  :tells the browser to create a variable

Syntax

We have 2 types of values i.e.
1.Literals (hardcoded value or constant value)
2.Values (varible values)

its a case sensetaive..

Var, VAR and var is different

Lastname and lastname are different.

var y;
var f,g,h;

f=g+h;
g=”P”+”a”;

Variables:

Variables are for storing the data value.
Variables must be unique.

Variables created without the keyword var, are always global.

Variable Rules:
Names can contain letters, digits, underscores, and dollar signs.
Names must begin with a letter
Names can also begin with $ and _ (but we will not use it in this tutorial)
Names are case sensitive (y and Y are different variables)
Reserved words (like JavaScript keywords) cannot be used as names

A variable declared without a value will have the value undefined.

2 types of Variables
1.Local Variable : can be access withing the block
2.Global Variable : can access through out the page

Operators:

= is the assignment operator and == is the equal operator

++ increment

— decrement

null === undefined // false
null == undefined //true

() operator invokes the function

Notes:
function without () will return the function definition instead of the function result

Data Type:

Primitive Data Type (normal data types which are without properties and methods)

String
Number
Bolean
Undefined
Null

Non Primitive Data Types:

Object
Array
RegExp

typeof undefined // undefined
typeof null // object

Function: for reusability of code

We invoke the function on

1. any event occurs (on click of user)
2. () from JavaScript code
3. Automatically (self invoked)

 

Events:

1. onchange
2. onclick
3. onmouseover
4. onmouseout
5. onkeydown
6. onload

Object:

var training = {
trainername: “Abel”,
skill : “Servicenow”,
id : 111,
trainerwithskill : function() {
return this.trainername + ” ” + this.trainername;
}
};

var t=training.trainerwithskill(); //function value
var t=training.trainerwithskill; //function defination
var t=training.skill;
var t=training[“skill”];