Explore

Javascript

Day 1

Lesson 1

⁠

Cheatsheet⁠

⁠

console is an object, a collection of data and actions

Printing

.log() function that can print

console.log()

Commenting

// for single line comments

/* words inside this are ignored */ - for documentation purposes

Data Types

number

bigint

string

boolean

null

undefined

symbol

object

→ All data types have access to specific properties such as

length for the number of characters in a string

console.log(’hotdog’.length) = 6

Operators works on numbers and also to strings just like python, basically concatenation adding string to another string

Add +

Subtract -

Multiply *

Divide /

Remainder %

dot operators, accesses the functions/methods innate for that data typecon

Methods

can be called with

a period (dot operator)

name of the method

opening and closing parentheses

e.g → ‘example string’.methodName()

Basic examples for string

startsWith()

toUppercase()

trim() → removes whitespace

Built-in objects (libraries for python)

⁠

Math methods⁠

examples

Math.random() → gives random number 0 to 1 (decimal), can be multiplied to any whole number

Math.floor() → rounds the number to nearest whole number

Math.ceil() → gives nearest integer

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Number methods⁠

⁠

Number.isInteger()

DAY 2

Variables

variables in JS cannot start with numbers

follow camel casing, small letter for first word

e.g. var favoriteFood = ‘pizza’

can be declared without values and be defaulted to contain ‘undefined’

var meal;

console.log(meal) \\outputs undefined

meal = ‘hotdog’

console.log(meal) \\outputs hotdog

Variable kinds

let - means can be assigned/re-assigned with different values

const - cannot be reassigned with a new value

Mathematical Operators with Variables

Basic calculate plus assign commands works

+=, -=, /=, *= → can be used using javascript and for let variables

Increment and Decrement operators

a++; or b—; works and will deduct or add 1 value to variables

String manipulation with variables

Concatenation

let favoriteAnimal = 'Dog';

console.log('My favorite animal: '+ favoriteAnimal);

String Interpolation

let myName = 'Ernest';

let myCity = 'Caloocan City';

console.log( `My name is ${myName}. My favorite city is ${myCity}`);

the key is to use caret to indicate that the thing to be printed is a template.

typeOF Operator

the equivalent of type() in python

let newVariable = 'Playing around with typeof.';

console.log(typeof newVariable);

Kelvin Weather Project ✅

Dog Years Project ✅

JS Versions: ES6 and Before

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