DEV Community: acobbina717

javaScript?.Fundamentals

acobbina717 — Mon, 15 Aug 2022 16:43:00 +0000

Here’s a few things to know when getting started with Javascript

Variables

Variables are used to store data, like the price of a item

let and const are used to declare variables

Variables declared with const can not be updated later in your code, variables declared with let can be updated throughout your code.
Use const to store data you don’t expect to change, like your first name

Console Log

console.log is used to view data in the terminal. console.log will be your best friend when you run into bugs. You will have the ability to log variables into the terminal to see where the error is coming from

What type of data can be stored in a variable?

JavaScript has 7 primitive data types & 1 non primitive data type

String

A sequence of text wrapped around double quotes: "", single quotes: '', or backticks: ``

If you’re storing a string with double quotes within, use single quotes or backticks

You can also add other variables into a string using string interpolation. To use string interpolation you must

wrap your string in backticks
add a dollar sign
add curly braces
write your variable inside of the curly braces

Number

A number is just a number, numbers do not need to be wrapped in quotes like a string.
Decimal numbers are called floats

Boolean

True or False.

undefined

Variables declared with no value will be undefined.
Variables declared with undefined will have a value of undefined

null

An empty or a unknown value
Unlike the undefined keyword we are defining a variable with a value of nothing.

Bigint

A number too larger to be stored in javascript's number data types

Symbol

A value that is unique and unchangeable

Non primitive data types / Collections of data

Object

Objects are written with curly brackets and hold {key : value} pairs..
An object's key is known as the property (the title of the value its attached to)
value can = any javascript data type | primitives and non primitives
We can use Dot Notation to access a objects property and we will get the value in return - ex: object.property

Array

Arrays are "list-like" objects that store multiple data types into a collection
Arrays are written with brackets [] and hold multiple data types that are separated by commas [1,"a",true,null]
Data in a array can be accessed individually by its index (numbered position in a list, javascript counts from 0) using bracket notation - ex: array[0]

Operators

Operators are symbols used to preform operations on values and variables.

Assignment Operator:

Used to assign values to variables =

Arithmetic Operators

Used to preform arithmetic calculations

Using += or any arithmetic, assignment operator combination pair will update our initial variables value += -= *= /= %=

Comparison operators

Used in logical statements to determine equality of values or variables, returns a true or false boolean value

The equal to operator (==) will convert strings into numbers and compare values regardless of data type
The strictly equal to operator(===) will only return true if both values are equal and have equal date types
The not equal to operator(!=) will n

Logical Operators

Used to determine the true or false logic between variables and values (&&) , (||), (!)

both values on each side of the and operator must be true for us to get a return value of true

String Operators

Add strings together. We can combine two strings into one using the + operator or the += operator

JAVASCRIPT FUNDAMENTALS PART 2... COMING SOON

Javascript Type Conversion in 3 mins

acobbina717 — Fri, 22 Jul 2022 20:37:00 +0000

I thought it might be cool to share with you how Javascript converts its primitive data types.
This is a high level overview of Javascript Type Conversion. After reading this blog you will have a better understanding of how javascript converts its data types

Type Conversion

Converting one data type to another ( Number to a String or String to a Number )

In Javascript there are two types of type conversion that happens, implicit conversion and explicit conversion. Let's go over both type of conversions.

Implicit Conversion

Javascript automatically converts data types without us telling it to.
Preforming arithmetic operations on two different data types with cause Javascript to convert the data types so it returns a valid value.
When using the + operator with a string and another data type, Javascript will convert both data types into strings and give a return value of a string.

console.log(5 + "5"); => "55"
console.log(true + "false"); => "truefalse"

When using the | - | * | / | % | operators Javascript will try to convert both data types into numbers

console.log(1 * "2"); => 2
console.log(5 * "5"); => 25

If a data type cant be converted into a number, Javascript will return NaN (Not A Number) as a return value

console.log(1 * "true"); => NaN
console.log(0 / false); => NaN
console.log(true % "false"); => NaN
console.log(1 * undefined); => NaN

When the boolean value of true is converted into a number, it has the value of 1

console.log(0 + true); => 1

The boolean value false is converted into a number, it has the value of 0

console.log(1 * false); => 0
console.log("14", true + false); => 1

null also has the value of 0

console.log(1 * null); => 0

Any number divided by 0 equals infinity

console.log(12 / false); => Infinity
console.log(true / false); => Infinity

Using equality operators will cause Javascript to convert data types
The == equals to operator compares both values and converts both data types into numbers
The === strictly equals to operator compares both values but does not convert data types

console.log(7 == "7"); => true
console.log(7 == "8"); => false
console.log(7 === 7); => true
console.log(7 === "7"); => false
console.log(7 === "8"); => false
console.log("true" == true); => false
console.log("true" === true); => false
console.log(true == 1); => true
console.log(true === 1); => false
console.log(null == undefined); => true
console.log(null === undefined); =>false

Explicit Conversion

Manually Converting Data Types
The Number() method converts string and boolean values into numbers. If a string contains any text, javascript will return NaN

console.log(Number("")); => 0
console.log(Number("Halo 3")); => NaN
console.log(Number("5")); => 5
console.log(Number(true)); => 1
console.log(Number(false)); => 0

The parseInt() method converts string values into whole numbers. parseInt() is a string method. It returns an error when used with other data types. If a string holds text and numbers, we can extract the numbers in a string only if the number is at the beginning of the string. If the number is not at the beginning of the string, we get a return value of NaN NotaNumber

console.log(parseInt("12")); => 12
console.log(parseInt("12.5")); => 12
console.log(parseInt(true)); => NaN
console.log(parseInt("true")); => NaN
console.log(parseInt("true12")); => NaN
console.log(parseInt("12true12")); => 12
console.log(parseInt(null)); => NaN

The parseFloat() method is similar to the parseInt() method except it is used to convert strings that hold decimal numbers into floats.

console.log(parseFloat("12.5")); => 12.5
console.log(parseFloat("2.5Hello")); => 2.5
console.log(parseFloat("2.5 Hello")); => 2.5
console.log(parseFloat("Hello2.5")); => NaN
console.log(parseFloat("Hello 2.5")); => NaN

The String() method and .toString() method converts primitive data types into strings

console.log(String(12)); => "12"
console.log(String(true)); => "true"
console.log(String(3.41)); => "3.14"
console.log((88).toString()); => "88"
console.log(true.toString()); => "true"
console.log((22.1).toString()); => "22.1"
console.log((12345678).toString()); => "12345678"

The Boolean() method converts primitive data types into boolean values
Positive & Negative numbers have a true value
0 and empty strings have a false value
Strings with text or numbers have true value
null & undefined has a false value

console.log(Boolean(3)); => true
console.log(Boolean(0)); => false
console.log(Boolean(-1)); => true
console.log(Boolean(-10)); => true
console.log(Boolean("")); => false
console.log(Boolean("ghjk")); => true
console.log(Boolean("56789")); => true
console.log(Boolean(null)); => false
console.log(Boolean(undefined)); => false