Learning space presentation1 learn Java script

Pseudocode
Pseudocode is an informal way of programming description that does not require any
strict programming language syntax or underlying technology considerations. It is
used for creating an outline or a rough draft of a program. Pseudocode summarizes a
program’s flow, but excludes underlying details. System designers write pseudocode
to ensure that programmers understand a software project's requirements and align
code accordingly.
Pseudocode is not an actual programming language.

The benefit of Pseudocode
• Pseudocode is understood by the programmers of all types.
It enables the programmer to concentrate only on the algorithm part of the
code development.
• Improves the readability of any approach. It’s one of the best approaches to
start implementation of an algorithm.
• Acts as a bridge between the program and the algorithm or flowchart. Also
works as a rough documentation, so the program of one developer can be
understood easily when a pseudo code is written out. In industries, the
approach of documentation is essential.
• The main goal of a pseudo code is to explain what exactly each line of a
program should do, hence making the code construction phase easier for the
programmer.

How to write Psuedo code
1. Arrange the sequence of tasks and write the pseudocode
accordingly.
2. Start with the statement of a pseudo code which establishes the
main goal or the aim. EX:
3. The way the if-else, for, while loops are indented in a program, indent the statements
likewise, as it helps to comprehend the decision control and execution mechanism. They
also improve the readability to a great extent.

Java script (JS)
• JavaScript is a dynamic programming language that's used for web development,
in web applications, for game development, and lots more. It allows you to
implement dynamic features on web pages that cannot be done with only HTML
and CSS.
• HTML and CSS are often called markup languages rather than programming
languages, because they, at their core, provide markups for documents with very
little dynamism.
• JavaScript, on the other hand, is a dynamic programming language that supports
Math calculations, allows you to dynamically add HTML contents to the DOM,
creates dynamic style declarations, fetches contents from another website, and
lots more.

Java script (JS)
How to Use JavaScript in HTML
Just like with CSS, JavaScript can be used in HTML in various ways
1. Inline JavaScript
you have the JavaScript code in HTML tags in some special JS-based attributes.
For example, HTML tags have event attributes that allow you to execute some
code inline when an event is triggered. Here's what I mean:
<button onclick="alert('You just clicked a button’)”>
Click me!
</button>

JS
2. Internal JavaScript, with the script tag
Just like the style tag for style declarations within an HTML page, the script tag
exists for JavaScript. Here's how it's used:
<script>
function(){ alert("I am inside a script tag") }
</script>

JS
3. External JavaScript
You may want to have your JavaScript code in a different file. External JavaScript allows this. For
such uses-cases, here's how it's done:

<script src="./script.js">
</script> // script.js alert("I am inside an external file");
The src attribute of the script tag allows you to apply a source for the JavaScript code. That
reference is important because it notifies the browser to also fetch the content of script.js.
script.js can be in the same directory with index.html, or it can be gotten from another website.
For the latter, you'll need to pass the full URL (https://.../script.js).

Variable declaration in JS
Variables in JavaScript
• Variables are containers for values of any data type. They hold values such that
when the variables are used, JavaScript uses the value they represent for that
operation.
• Variables can be declared and can be assigned a value. When you declare a
variable, you're doing this:
let name;
• Here's what it means to assign a value to a variable:
let name; name = "JavaScript";
• Declarations and assignments can be done on one line like so:
let name = "JavaScript";
name has been declared, but it doesn't have a value yet.

function print()
{
console.log(name);
console.log(age);
var name = "JavaScript";
let age = 5;
}
print();
On calling the print function (print()), the
first console.log prints undefined while the second console.log throws
an error that it "Cannot access age before initialization".
function print()
{
var name;
console.log(name);
console.log(age);
name = "JavaScript";
let age = 5;
}
print();

• The var operator. You can declare variables and assign values to
them which can be changed later in the code.
var name = "JavaScript";
name = "Language";
• The let operator: this is also very similar to var – it declares and
assigns values to variables that can be changed later in the code.
The major difference between these operators is that var hoists
such variables, while let does not hoist

Data types in JS
Different types of variable can be identified:
• Number (for example, 6, 7, 8.9): on which you can apply arithmetic operations (like
addition) and many more
• String (like "javascript", 'a long sentence', a short paragraph): anything found between
single quotes ('...'), double quotes ("...") and backticks (...). There's no difference
between single and double quotes
let str = `I am a multiline string`;
• Boolean (can only be of two values: true or false): more like yes (true) or no (false)
• Array (for example, [1, 2, "hello", false]): a group of data (which can be of any type,
including arrays) separated by a comma. Indexing starts from 0. Accessing the
content of such a group can be like so: array[0]
• Object (for example {name: 'javascript', age: 5}): also a group of data but in the form
of a key:value pair. The key has to be a string, and the value can be any type including
another object. Accessing the content of the group is done with the key, for
example obj.age or obj["age"] will return 5.

Data types in JS
• Undefined (the only data this type supports is undefined): This data
can be assigned to a variable explicitly, or implicitly (by JavaScript) if
a variable has been declared but not assigned a value. Later in this
article, we'll look at variable declaration and value assignment.
• Null (the only data this type supports is null): Null means there is no
value. It holds a value, but not a real value – rather, null.
• Function (for example, function(){ console.log("function") }): A
function is a data type that invokes a block of code when called.
More on functions later in this article.

Comments in JS
Comments in JavaScript
Just like HTML, sometimes we may want to put a note beside our code
which does not need to be executed.
We can do this in JavaScript in two ways:
• with single-line comments, like this:
// a single line comment
• or with multi-line comments, like this:
/* a multi line comment */

Functions in JS
Functions in JavaScript
With functions, you can store a block of code that can be used in other places in your
code. Say you wanted to print "JavaScript" and "Language" at different places in your
code. Instead of doing this:

Naming Conventions in JS
1. Naming Convention for variables:
JavaScript variable names are case-sensitive. Lowercase and uppercase letters are distinct.
var DogName = 'Scooby-Doo’;
var dogName = 'Droopy’;
var DOGNAME = 'Odie’;
2. Naming Convention for Booleans
When it comes to Boolean variables, we should use is or has as
prefixes
// bad var bark = false;
// bad var ideal = true;
// bad var owner = true;
// good var isBark = false;
// good var areIdeal = true;
// good var hasOwner = true;

3. Naming Convention for Functions
JavaScript function names are also case-sensitive. So, similar to variables, the camel
case approach is the recommended way to declare function names.
// bad function name(dogName, ownerName)
{
return '${dogName} ${ownerName}’;
}
// good function getName(dogName, ownerName)
{
return '${dogName} ${ownerName}’;
}

4. Naming Convention for Constants
JavaScript constants are also case-sensitive. However, these constants
should be written in uppercase
var LEG = 4; var TAIL = 1;

Java script Arithmetic Operator
Operator Description
+ Addition
- Subtraction
* Multiplication
** Exponentiation (ES2016)
/ Division
% Modulus (Remainder)
++ Increment
-- Decrement

Java script arithmetic operator
Incrementing
Let x=5;
X++;
Decrementing
Let x=5;
X++;
Exponentiation
Let x=5;
Let z= x**2;
let x = 5;
let z = Math.pow(x,2);

Operator Precedence
Let x=100+50 *3;
Let x= (100+50)*3;
Let x=100+50-3;

// Assign values to x and y
let x = 10;
let y = 20;
// Add x and y and assign the sum to z
let z = x + y;
console.log(z);
Answer = 30

Answer = 10
let x = 10;
let y = 20;
// Subtract x from y and assign the difference to z
let z = y - x;
console.log(z);

Answer = 11
let x = 1 + "1";
console.log(x);
typeof x;

Answer = 100
let x = 20;
let y = 5;
// Multiply x by y to get the product
let z = x * y;
console.log(z);

Answer = 4
let x = 20;
let y = 5;
// Divide y into x to get the quotient
let z = x / y;
console.log(z);

Answer = 0
9 % 3;
10 ** 5;
Answer = 10*10*10*10*10= 100000

Assignment operator
Operator Example Same As
= x = y x = y
+= x += y x = x + y
-= x -= y x = x - y
*= x *= y x = x * y
/= x /= y x = x / y
%= x %= y x = x % y
<<= x <<= y x = x << y
>>= x >>= y x = x >> y
>>>= x >>>= y x = x >>> y
&= x &= y x = x & y
^= x ^= y x = x ^ y
|= x |= y x = x | y
**= x **= y x = x ** y

String Concatenation
How to concatenate strings in Java script.
There are different ways to do this:
The + Operator
onst str = 'Hello' + ' ' + 'World'; str; // 'Hello World’
String#concat()
JavaScript strings have a built-in concat() method.
let text1 = "sea";
let text2 = "food";
let result = text1.concat(text2);
let text1 = "Hello";
let text2 = "world!";
let result = text1.concat(" ", text2);

JavaScript Comparison and Logical Operators
Operator Description Example
== Equal to X==5
=== Equal value and equal type X===5
!= Not equal X!=3
!== Not equal value or not equal
type
X!==3
> Greater than X>3
< Less than X<3
>= Greater than or equal X>=5
<= Less than or equal X<=5

Condition statements
• Use if to specify a block of code to be executed, if a specified condition is true
• Use else to specify a block of code to be executed, if the same condition is false
• Use else if to specify a new condition to test, if the first condition is false
• Use switch to specify many alternative blocks of code to be executed
if (condition) {
// block of code to be executed if the condition is
true
}
if (hour < 18) {
greeting = "Good day";
}

Else-statement
if (condition) {
true
} else {
false
}
if (hour < 18) {
} else {
greeting = "Good evening";
}

Else if statement
if (condition1) {
// block of code to be executed if condition1 is
true
} else if (condition2) {
// block of code to be executed if the condition1 is
false and condition2 is true
} else {
// block of code to be executed if the condition1 is
false and condition2 is false
}
if (time < 10) {
greeting = "Good morning";
} else if (time < 20) {
} else {
greeting = "Good evening";
}

Which editor can be used to write JS?
Atom
Visual Studio Code
Brackets

Learning space presentation1 learn Java script

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