Basic Programming Cheat Sheet

A Programming › JavaScript cheat sheet in English by tegdsd12

Basic Programming 1111

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PRs

Variable Instantiation

let variableName = value
let	required keyword to initialize a variable
variableName	arbitrary name, no spacing, must contain letter, no punctuaction, cannot use reserved keywords, camel-cased
=	assign
value	any data type
camel-case	no spacing between words, every word except the first is capitalized e.g a red balloon -> aRedBalloon

the value assigned can be referenced in later parts of the program through variableName.
Only one value can be assigned to one variable, i.e one instantiation per variable, if let var1 = 'string' previously, cannot let var1 = 2 again later in the code

Operators

+	plus
-	minus
*	multiply
/	divide (5/2 = 2.5)
%	remainder (5 % 2 = 1)
>	more than
<	less than
>=	more than or equals
<=	less than or equals
i++	i = i + 1
i--	i = i - 1
==	equal value
===	equal value and data type
i (+,-,*,/) = value	shorthand for i = i + value, i= i - value, etc

Data Types

String	'string'	Anything in quotes. If there are quotations inside the string, use a different type of quotation ( ' and " )
Number	1, 23, 400	number
Boolean	true, false	true/false value
Character	'a', '2'	single input
Undefined	let variable	variable instantiated but not assigned a value
Null		variable not defined(instantiated)

Array

['string', 2, true]

- initialized with square brackets
- can contain all data types, including arrays and objects
- ordered list of values, starting from index 0 to refer to first element
- get item in array by referring to its index (array[0] gets 'string', array[1] gets 2)

Object

let object = { key1: value1, key2: value2 }

similar to array, but replace index with key(string)
can contain all data types, including arrays and objects
refer to objects in 2 ways
1. object.key1 gets value1
2. object['key2'] gets value2. when using square brackets, put the key in string format

Function Example

let num1 = 1;
let num2 = 20;
let result = addTogether(num1, num2);

num1 and num2 becomes firstNum and secondNum respectively
if no return value, calculations done in the function cannot be carried out of the function

function addTogether(firstNum, secondNum) {
return firstNum + secondNum;
}

result will get the returned value of 21

Loops

if	if condition is true, execute block
else	must be used with if, executes if if condition is false
if else	additional if statements after the first if statement
while	while condition is true, keep executing block
for	for (let i = 0; i< 10; i++), a condensed while loop
for	for (let number of numbers)
for	for (let number in numbers)

loop (condition) {
execute code in block
}

for

for has multiple uses
1.a condensed while loop
for (let i = 0; i< 10; i++) {}
2. To loop through an array/object
let numbers = [20, 30, 10, 50, 70];
for (let number of numbers) {
use value
each loop uses number = 20, then 30, 10 ...
}
for (let numbers in numbers) {
use index/key
each loop uses number = 0, then 1, 2 ...
to get value, use numbers[number] (object[index])
}

Function

function foo(param1, param2) { return param1 + param2}
function	keyword to instantiate function
foo	function name, use to describe function purpose, camel-case
param1, param2	parameters to put into function (optional)
return	value to get back from function (optional)

functions are called with brackets -> foo()
if function has parameters, function must be called with parameters -> foo(param)
parameters are assigned to new names for usage in the function (see below)

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