Uki.life

08.05.2017.

Monday.

Today we learned Javascript.

⟹Javascript introduction

➡Javascript statements are separated by semicolons.

➡Numbers are not allowed as the first charector.

➡All javascript identifiers are case sensitive.

⟹It has different cases

➡Hyphens - first-name, last-name

➡Underscore - first_name, last_name

➡Upper camel case (Pascal case) - FirstName, LastName

➡Lower camel case - firstName, lastName

⟹Javascript charactor set

➡Javascript uses the Unicode character set.

➡Unicode covers all the characters , punctuations , and symbols in the world.

⟹Javascript statements

➡Values
➡Operaters
➡Expressions
➡key words
➡comments

Javascript statements are separated by semi colons.

Strings ⟹ "John Doe"   or   'John Doe'

Variables are used to store data values.
var   ⟹ Key word to declare variable.
=     ⟹    Assign value to variable.

Arithmatic operaters ⟹ + , - , * , /

⟹Javascript comments

//I will be executed ⟹ Single line command
/* I will be executed.
I will be executed. */ ⟹ Multi line command

Numbers are not allowed the first charector.But first charector must be a letter or under score(_) or a doller sign($).

Javascript is a case sensitive

Example:firstname , firstName ⟹ There are not same values.

⟹Javascript can change

HTML content ⟹ Hi ➝ Hello
HTML attributes ⟹ Turn on ➝ Turn off

⟹Javascript display possibilities

1)Writing into an HTML elements using ⟹ inner.html()

2)Writing into an HTML elements using output ⟹ document.write()

3)Writing into an HTML elements using alert box ⟹ window.alert()

4)Writing into an HTML elements using browser console ⟹ console.log()

⟹JavaScript Data Types

JavaScript variables can hold many data types

➡numbers
➡strings
➡objects
➡booleans
➡arrays

⟹JavaScript Functions

➡A JavaScript function is defined with the function keyword, followed by a name, followed by parentheses ().

➡Function names can contain letters,
digits,
underscores,
and dollar signs
(same rules as variables).

➡The parentheses may include parameter names separated by commas:
(parameter1, parameter2, ...)

➡The code to be executed, by the function, is placed inside curly brackets: {}

function name(parameter1, parameter2, parameter3) {
code to be executed
}

➡Function parameters are the names listed in the function definition.

➡Function arguments are the real values received by the function when it is invoked.

➡Inside the function, the arguments (the parameters) behave as local variables.

⟹Function Invocation

➡The code inside the function will execute when "something" invokes (calls) the function:

➡When an event occurs(when a user clicks a button)
When it is invoked from JavaScript code
Automatically

⟹Function Return

➡When JavaScript reaches a return statement, the function will stop executing.

➡If the function was invoked from a statement, JavaScript will "return" to execute the code after the invoking statement.

➡Functions often compute a return value. The return value is "returned" back to the "caller"

var x = myFunction(4, 3); // Function is called, return value will end up in x function myFunction(a, b) {
return a * b; // Function returns the product of a and b }

⟹Why we use functions

You can reuse code:

Define the code once, and use it many times.

You can use the same code many times with different arguments, to produce different results.

⟹The () Operator Invokes the Function

Using the example above, toCelsius refers to the function object, and toCelsius() refers to the function result.

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

JavaScript Objects

⟹Object Properties

The name:values pairs (in JavaScript objects) are called properties.

var person = {firstName:"John", lastName:"Doe", age:50, eyeColor:"blue"};

⟹Accessing Object Properties

You can access object properties in two ways:

objectName.propertyName

objectName["propertyName"]

⟹Accessing Object Methods

You access an object method with the following syntax:

objectName.methodName()