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Basic Programming Cheat Sheet by

Basic Programming 1111

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

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

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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