JavaScript Study General

JavaScript Study General Nov 19, 2024 18:01:11 GMT nickyslicky likes this

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Post by Geist on Nov 19, 2024 18:01:11 GMT

The below is a general coding guide (leaning toward Javascript) written by Ace, a member of the community who hates me and doesn't want to make a forum account for me to tag I guess. He's given me permission to share:

Introduction

So you've decided to pick up Javascript? My condolences. Fortunately, Javascript's one redeeming feature is that it is very easy to use, however I'm going to ignore Javascript for the most part and just explain the basics of coding. I'll make sure to point out where Javascript does things differently if possible

Basics

First things first, code is sequential, meaning each line runs in order one after another

functionA(); // This line will run first
functionB(); // Then this line
functionC(); // Finally this line

Next lets address the
;
at the end of those lines. In most coding languages, this is used as a terminator for an instruction, but not necessarily the end of a line

// Sometimes you can have multiple instructions on one line
functionA(); functionB(); functionC();

// and other times one function might take up multiple lines
function(
    parameter1,
    parameter2,
    parameter3
);

NOTE ‼️ Javascript Nonsense

Javascript doesn't particularly care about the semicolon, it compiles fine with or without it, but I'd advise using it regardless to develop the habit for other coding languages which do

Finally we need to talk about

{
these things

}

int foo;

// These denote a "scope"
// Things outside the scope can be accessed in the scope, but things in the scope cannot be accessed outside the scope
{
    int bar;

    // Inside the scope we can access both "foo" and "bar"
}

// Outside the scope we can only access "foo", even though "bar" has been defined already

Now onto making stuff do things

Variables

Think of variables like boxes which store things. To use a variable, you first have to declare it, like so:

int foo; // This is a variable called "foo", which can be given a value later but will default to 0 for now

foo = 2; // '=' is used to assign a value to a variable

int bar = 4; // This is a variable called "bar", which is given a value as soon as it is created ( this is called "inline assignment" )

// NOTE: Variable names must be alphanumeric and contain no spaces

As you can see, these variables are both of type

int
To use the analogy of boxes and storing things, a variable's type determines what shape the box is and therefore what kind of things it can store. There are a few base types you should know about, but know that variables can store just about anything ( classes, structs and enums to name a few but don't worry about those yet )

bool a = true; // This is a boolean, which can store true/false values
int b = 128; // This is an integer, which can store whole numbers both positive and negative
float c = 3.14; // This is a float, which can store decimal numbers both positive and negative ( sometimes these values need to be postfixed with an 'f', eg. 3.14f )
char d = 'j'; // This is a char, which can store single characters
string c = "hello world!"; // This is a string, which can store text ( behind the scenes its actually just a load of char variables in a trenchcoat )

NOTE ‼️ Javascript Nonsense

Javascript doesn't require you to declare the exact type of a variable and this is referred to as being "weakly-typed". Instead, Javascript has 2 keywords for declaring variables, var and let
both of which can accept any value

let jeff = 2;
jeff = "hello world!";
jeff = false

While you can assign any value to a Javascript variable, I'd recommend avoiding assigning different types to the same variable as it can get confusing and overly complicated
I'd also recommend avoiding using

var
as it can lead to bad coding practices for reasons I can explain if you really want to know, but just trust me on this one and use

let
instead because it functions more like variables in other coding languages

[!] Test your knowledge

Declare a variable with the correct type to hold the value "lol short" using whatever name comes to mind

SPOILER: Click to show

Answer:
string yourVariableName = "lol short";

Operators

Operators allow you to compare and calculate with variables and values. Operators work using two values (with some exceptions) and can be optionally surrounded with

(
parenthesis

)
for organization, just like a mathematical equation

int a = 2;
int b = 4;

// Mathematical operators allow you to calculate things using ints and floats
int add = (a + b); // '+' will add two values together
int sub = (a - b); // '-' will subtract one value from the other
int div = (a / b); // '/' will divide one value by the other
int mul = (a * b); // '*' will multiply one value by the other

// If you want to put the result into one of the operation variables, you can do so by using the operator and '=' like so
int a += b; // Add the value of 'b' to 'a'

// Increment and decrement allow you to modify the value of a variable inline

++a; // Increment the value by 1
--b; // Decrement the value by 1

// Comparison operators allow you to compare things and output boolean values
bool equal = (a == b);      // EQUAL outputs true if the values are identical
bool notequal = (a != b);   // NOT EQUAL outputs true if the values are different
bool greaterthan = (a > b); // GREATER THAN outputs true if 'a' is larger than 'b'
bool lessthan = (a < b);    // LESS THAN outputs true if 'a' is smaller 'b'

// Some comparison operators only work with boolean values
bool and = (g && h); // AND outputs true if both values are true
bool or = (g || h); // OR outputs true if either value is true
bool not = !g;       // NOT outputs the opposite of the value (g = false so m = true)

// NOT can also be used on operators in brackets to invert the whole statement
bool bignot = !(a == b); // 'a' does not equal 'b', but NOT inverts the result to true

// Operators can be combined to form complex equations
int complexmath = ((a + b) / c);
bool complexbool = ((a == b) && (a > 5));

[!] Test your knowledge

Using boolean values of

a
,

b
and

c
( their values don't matter ), make a new boolean

d
equal true when

a
and

b
or not

c
are true

SPOILER: Click to show

Answer:
bool d = ((a && b) || !c);

Functions

A function does stuff, plain and simple ... it'll make more sense in a minute

// This is a function definition, it defines what a function does
void someFunction()
{
    // Do Stuff
}

// This is a function call, it makes the function actually do things
someFunction();

As you can see, this function is pretty empty, but I have two more things to explain before I show you a working example

// This function has a parameter, which allows you to pass information into it
// Parameters can only be used inside the function they are part of
void functionOne(int param)
{
    // Do stuff
}

// This function has a return value, which allows it to pass information back
// The previous examples use "void", which just means it doesn't have a return type
int functionTwo(int param)
{
    // Do stuff
    return 0; // to return a value, we use "return" ... its pretty self explanatory
    // return will also immediately exit the function, so anything after it is ignored
}

// return can also be used without a value in a void function to immediately exit

So now we have the basics of functions down, lets make a simple one. How about one which takes two values, adds them together, then returns the result?

// Define the function
int addition(int paramOne, int paramTwo)
{
    return (paramOne + paramTwo);
}

// Declare some variables
int a = 5;
int b = 10;
int c; // c is equal to 0

// Call the function
c = addition(a, b); // c is now equal to 15 ( a + b )

NOTE ‼️ Javascript Nonsense

Javascript doesn't require you to declare the return type of a function or its parameters

someFunction(param)
{
    // I hate this part of Javascript
    return literallyAnythingUnderTheSun;
}

Like with variables, try and avoid returning different types from the same function or passing different types to the same parameter. It might help to use inline comments to remind yourself what types are expected

/*int*/ someFunction( /*int*/ param )
{
    // Do Stuff
    return anIntLikeANormalPerson;
}

[!] Test your knowledge
Make a function which takes two integers and multiplies the first by the second, then returns the result

SPOILER: Click to show

Answer:

int yourFunctionName(int paramOne, int paramTwo)
{
    return (paramOne * paramTwo);
}

Flow Control

Sometimes we only want code to run if a certain condition is met. Sometimes we want code to run multiple times. Sometimes we need to fork based on some information. Lets explore that

NOTE ‼️ Semicolon

When writing flow control statements, a semicolon is not required at the end of the line
The code inside the flow control statement still needs them though

if

The most important flow control, the if statement, only executes code if its condition is satisfied

if(condition) // Conditions are always expecting a boolean value
{
    // This part executes if the condition is true
}

[!] Test your knowledge
Declare a boolean variable, then make an if statement which uses the boolean as its condition

SPOILER: Click to show

Answer:

bool yourVariableName; // The value of the boolean does not matter for this exercise
if (yourVariableName)
{
    // Some code
}

for

This one will drive you loopy; for statements allow you to run some code for a specified number of cycles ( referred to as "loops" )

// Declare a loop variable, evaluate the loop condition, then define the step
// Loop condition must be true for the loop to continue
// Step defines how the loop value changes each iteration
for(declare; condition; step)
{
    // This part executes every time the loop iterates
}

for(int i = 0; i < 10; ++i) // Loop while i is less than 10, i goes up by 1
{
    // Do Stuff
    // This loop runs 10 times (0, 1, 2 ... 8, 9) because it stops when it hits 10
}

for(int i = 0; i < 10; i += 2) // Loop while i is less than 10, i goes up by 2
{
    // Do Stuff
    // This loop runs 5 times (0, 2, 4, 6, 8) as it stops when it hits 8
}

There is another way to use a loop, but its only used with something I haven't taught you yet so don't worry about it

[!] Test your knowledge

Make a loop which will run 10 times, but steps by 2 each iteration

SPOILER: Click to show

Answer:

for(int i = 0; i < 20; i += 2;)
{
    // Some code
}

while

Its been a while since I've used this one, but while statements will check a condition, run the code inside them, then repeat this process until the condition is no longer true

while(condition) // The loop iterates as long as the condition is true
{
    // This part executes every time the loop iterates
}

There is also the do ... while statement, which will run the code at least once before checking the condition. Think of it like a shoot-first-ask-questions-later affair, we do some code first then check the while condition and loop if its true

do
{
    // This part executes every time the loop iterates
}
while(condition); // The loop iterates as long as the condition is true
// Unlike other flow control statements, a do ... while needs a ; after it

[!] Test your knowledge

Make a while loop which runs at least once with a boolean variable as it's condition. The loop body should set the variable to false

SPOILER: Click to show

Answer:

bool yourVariableName = true;
do
{
    yourVariableName = false;
}
while(yourVariableName);

Overhead

Knowing how to use variables, operators and functions is great but also useless unless you know how to structure a program. Unfortunately, this is where a lot of languages diverge, so I'll show the ones I know. This section is hard to simplify and I'll try my best, but it will be quite technical in some areas

Javascript

Javascript is simple, you just start declaring variables and functions and ( provided you have an environment like node.js to run it ) it just works

// Program.js
let foo = 2;
let bar = 4;
let foobar = (foo + bar);

if(foobar > 5)
{
    console.log(foobar); // This outputs the value of foobar to the console
}

C++

C++ however is an "object-oriented" language which uses "classes" to hold functions and variables, but we can learn about those later. To start a c++ program, a global ( not contained inside a class ) function called "main" with an

int
return type (used for the error code on exit) is needed. Everything to do with your program starts in here and eventually ends in here too

// Program.cpp
// "includes" go up here to allow you to use the content of other files

int main()
{
    // Your entire program goes here
    
    return 0; // An error code of 0 means the program exited successfully
}

In practice, the main function will usually just spawn a few classes, possibly setup an update loop, and let them handle the running of the program. But in this case, our simple program can go directly into the main function

// Program.cpp
include <iostream> // This allows us to input from or output to the console

int main()
{
    int foo = 2;
    int bar = 4;
    int foobar = (foo + bar);

    if(foobar > 5)
    {
        // When using functions from classes/namespaces, you use class::function
        // "std" is the class/namespace and "cout" is the function
        // cout is short for "Console OUTput", cin would be the opposite
        std::cout << foobar;
    }

    system("pause"); // Lazy hack to make the console wait for an input before closing
    return 0;
}

The Moon Shade

Rules & Info

Post by Geist on Nov 17, 2024 6:12:07 GMT

Post by Geist on Nov 17, 2024 6:19:44 GMT

Post by Geist on Nov 19, 2024 18:01:11 GMT

if

for

while

Javascript

C++

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