Javascript gives html designers a programming tool


JavaScript gives HTML designers a
programming tool - HTML authors are normally
not programmers, but JavaScript is a scripting
language with a very simple syntax! Almost
anyone can put small "snippets" of code into
their HTML pages

JavaScript can put dynamic text into an HTML
page - A JavaScript statement like this:
document.write ("<h1>" + name + "</h1>")
can write a variable text into an HTML page

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What can a JavaScript Do?

33
What can a JavaScript Do?
JavaScript variables can hold:

Numbers: integer and floating point

Booleans: true, false

Strings: "Hello World!"

Objects: myObj = new Object();

Null: empty, no value

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What can a JavaScript Do?
JavaScript Operators

The usual range of comparison and
arithmetic operators.

String concatenation with +: "Age:" +
"20" gives "Age: 20 "

C style conditional operators:
preferredPet = (cats > dogs) ? "felines" : "canines"

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JavaScript
Web servers
Web browser
Request
HTML page
with JavaScript
JavaScript
response

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JavaScript variables
JavaScript variables are used to hold values
or the results of expressions.
Declare variables
var x=5; // after execution x has value 5, or use x=5 ;
var carname="Volvo";
Rules for JavaScript variable names:

Variable names are case sensitive (y and Y are two different variables)

Variable names must begin with a letter or the underscore character followed by
letters, digits or underscore character

Avoid reserve words which have special meanings in the programming
language, like for , var , while and function

Give memorable and meaningful names, like age, name, subject, carname etc

;
;

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JavaScript variables
Special characters – they all begin with a
backslash character (\)
Output Character Special Code to Use
Backslash (\) \\
Double quote (") \"
Single Quote (‘) \’
Tab \t

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JavaScript operators
operators types

Mathematical

Assignment

Comparison

Logical

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JavaScript operators
Given y=8, the following table explains mathematical
operators
operator description example Result of x
+ Addition x=2+3 5
- Subtraction x=y-5 3
* Multiplication x=y*2 16
/ Division x=y/2 4
% Modulus (division
remainder)
x=y%3 2
++ Increment x=++y 9
-- Decrement x=--y 1