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- // this worksheet was generated from the 'Javascript Language Fundamentals' section of Brad Traversy's Modern Javascript Udemy course
- // Variables **********************************************************************
- // name 3 keywords for initializing and declaring a variable? var, let, const
- // which 2 JS variable keywords are block scoped? let and const
- // declare a variable but don't initialize a value.
- // let name
- // console.log(name)
- // assign the initialized variable a value.
- // name = 'John Doe'
- // console.log(name)
- // which type of JS variable must be both declared and initialized at the same time? constant
- // JS variables can contain what? letters,numbers,underscores,and $
- // JS variables connot start with what? numbers
- // Multi-word-vars. Give an example of Comel case, Underscore, and Pascal case. which should you in JS? camelcase: firstName, underscore: first_name, pascal: FirstName
- // when using const in JS, are mutatable data structures such as arrays and abjects, still mutatable? yes
- // Data-Types ************************************************************************
- // Name the six primitive data types in JS:
- // string
- // number
- // boolean
- // undefined
- // null
- // symbol
- // (true or false) Null is an intentional empty value? true
- // (true or false) Undefined is variable that has not been assigned a value? true
- // (true or false) arrays, Object Literals, Functions, and Dates are considered Reference Data Types? true
- // what can be used to find out a variable's type? typeof()
- // Type conversion *******************************************************************
- // Use the String function to convert a number, boolean, date, and an array to a string
- // let item = 5
- // item = true
- // item = ['mon', 'tues', 'wed']
- // item = new Date()
- // item = String(item)
- // console.log(item)
- // console.log(typeof item)
- // Use the toString method to convert a number to a string
- // let item = 8
- // item = item.toString()
- // console.log(item)
- // console.log(typeof item)
- // Use the Number function to convert a string-number, both booleans, and a word string to a number
- // let it = '9'
- // it = true
- // it = false
- // it = 'word'
- // it = Number(it)
- // console.log(it)
- // console.log(typeof it)
- // (true or false) NaN is a value that means not a number. true
- // (true or false) NaN is what is output when a value can't be converted to a number. true
- // besides the Number() function, show 2 more ways to convert to a number, using the functions parseInt() and parseFloat()
- // it = '33'
- // it = '39.3376'
- // it = parseInt(it)
- // it = parseFloat(it)
- // console.log(it, typeof it)
- // console.log(it.toFixed(2), typeof it)
- // (true or false) the toFixed method can be used to add decimal places to a number. true
- // Type coersion *******************************************************************
- // (true or false) type coersion is when JS automatically does type conversion on a value. this can be unwanted, so you need to be alert to this possibility when coding? true
- // The Math Object *****************************************************************
- // use the following methods on the Math object to generate results.
- // Math.round()
- // Math.ceil()
- // Math.floor()
- // Math.sqrt()
- // Math.abs()
- // Math.pow()
- // Math.min()
- // Math.max()
- // Math.random()
- // let num
- // num = Math.round(12.7)
- // num = Math.ceil(12.1)
- // num = Math.floor(12.9)
- // num = Math.sqrt(64)
- // num = Math.abs(-59)
- // num = Math.pow(8, 2)
- // num = Math.min(64, 55, 33)
- // num = Math.max(64, 55, 33)
- // num = Math.random() * 100
- // num = parseInt(num)
- // console.log(num)
- // String methods & Concatenation ******************************************************
- // give an example of string concatenation
- // let name = 'Tom'
- // let secondName = 'Smith'
- // console.log(name + ' ' + secondName)
- // append 2 string variables using the += (addition assignment operator) which means x = x + y
- // name += secondName
- // console.log(name)
- // give an example of escaping characters
- // let phrase = 'Tom replied: Let\'s study at my house'
- // console.log(phrase)
- // use the following methods and properties on strings
- // length
- // let email = 'john@yahoo.com'
- // console.log(email + ' is ' + email.length + ' letters long.')
- // concat()
- // let work = ' driver'
- // console.log(email.concat(work))
- // toUpperCase()
- // console.log(email.toUpperCase())
- // toLowerCase()
- // let caps = 'HELLO'
- // let smalls = caps.toLowerCase()
- // console.log(smalls)
- // get character using []
- // console.log(smalls[2])
- // indexOf()
- // let big = 'supercalafragilistic'
- // console.log(big.indexOf('c'))
- // // lastIndexof() (this comes from the end of the string)
- // console.log(big.lastIndexOf('c'))
- // // charAt()
- // console.log(big.charAt(9))
- // // Get last character of a string by using charAt(yourstring.length -1)
- // console.log(big.charAt(big.length - 1))
- // // substring(0, 4)
- // let sub = big.substring(0, 4)
- // console.log(sub)
- // // slice(0, 4) slice works with strings and arrays... with slice you can use negative numbers and it will begin at the back of the string or array
- // let slice = big.slice(0, -4)
- // console.log(slice)
- // split() split will turn the string into an array. you can split on any character including spaces.
- // let phrase = 'this is my string'
- // let newPhrase = phrase.split(' ')
- // console.log(newPhrase)
- // // replace()
- // console.log(phrase.replace('my', 'your'))
- // // includes() check if the string or char exists inside of a string. returns true or false
- // console.log(phrase.includes('string'))
- // // Template Literals *****************************************************************
- // // take the following data and input it as an unordered list in html (do this using string concatenation and template literals)
- // const obj = {
- // name: 'John',
- // age: 30,
- // job: 'Web Developer',
- // city: 'Miami'
- // }
- // let concat = '<ul> <li>name: ' + obj.name + '</li> <li>age: ' + obj.age + '</li> <li>job ' + obj.job + '</li> <li>city: ' + obj.city + '</li> </ul>'
- // console.log(concat)
- // let data = `<ul>
- // <li>name: ${obj.name}</li>
- // <li>age: ${obj.age}</li>
- // <li>job: ${obj.job}</li>
- // <li>city: ${obj.city}</li>
- // </ul>`
- // console.log(data)
- // // output an expression using template literals
- // let add = `5 + 5 = ${5 + 5}`
- // console.log(add)
- // // output a function using template literals
- // const hello = function () {
- // return 'hello'
- // }
- // const literal = `I'm literally saying ${hello()}`
- // console.log(literal)
- // // output conditional or 'if statement' using template literals. You must use ternary operator syntax or wrap the 'if statement in a called anonymous function
- // let age = 40
- // let sentence = `Bob is ${age < 39 ? 'young' : 'old'}`
- // console.log(sentence)
- // // ex. ternary-operator: `${age > 30 ? 'Over 30' : 'Under 30'}
- // // ex. invoked anon function if-statement:
- // // const age = 30
- // // let html = `<div>
- // // ${
- // // (age => {
- // // if(age > 30) {
- // // return 'Over 30'
- // // } else {
- // // return 'Under 30'
- // // }
- // // })()
- // // }
- // // </div>`
- // // document.body.innerHTML = html
- // let sentence2 = `Bob is ${
- // (age => {
- // if (age < 39) {
- // return 'young'
- // } else {
- // return 'old'
- // }
- // })()
- // }`
- // console.log(sentence2)
- // Arrays and Array Methods *************************************************************
- /* ~~~~~~~~~~~~ examples
- ex. const numbers = [43,56,13,81,61]
- ex. const numbers2 = new Array(22,45,33,17,12)
- ex. numbers.length
- ex. Array.isArray(numbers)
- ex. numbers[3]
- ex. numbers[2] = 100
- ex numbers.indexOf(61)
- ex. numbers.push(250)
- ex. numbers.unshift(120)
- ex. numbers.pop()
- ex. numbers.shift()
- ex. numbers.splice(1,1)
- ex. numbers.reverse()
- ex. numbers.concat(numbers2)
- ex. fruit.sort()
- ex. numbers.sort()
- ex. numbers.sort(function (x, y){
- return x - y
- })
- ex. numbers.sort(function (x, y){
- return y - x
- })
- ex. finds the 1st number under 50
- function under50(num) {
- return num < 50
- }
- numbers.find(under50)
- ex. finds the 1st number over 50
- function overr50(num) {
- return num > 50
- }
- numbers.find(over50)
- ~~~~~~~~~~~~~~~~~~~~~~~~~ */
- // // create an array using an array literal:
- // const list = ['eggs', 'bacon', 'ham', 'bread']
- // console.log(list)
- // // create an array using an array constructor:
- // const groceries = new Array('eggs', 'bacon', 'tomatoes', 'gravy')
- // console.log(groceries)
- // // Create some arrays with numbers, strings, mixed data types:
- // const nums = [3, 5, 17, 33]
- // const strings = ['rock', 'opera', 'bluegrass', 'country', 'hip-hop']
- // const mixed = [7, 'eleven', {car: 'chevy'}, ['stop', 'drop', 'roll'], 79, true, null, 'end']
- // console.log(nums)
- // console.log(strings)
- // console.log(mixed)
- // // Get array length:
- // console.log(mixed.length)
- // // Check if is array:
- // console.log(Array.isArray(mixed[3]))
- // // Get single value:
- // console.log(nums[2])
- // // Insert into array:
- // nums[2] = 19
- // console.log(nums)
- // // Find index of value:
- // let singleNum = nums.indexOf(33)
- // console.log('index: ', singleNum)
- // // ------MUTATING ARRAYS----------
- // // Add on to end:
- // nums.push(99)
- // console.log(nums)
- // // Add on the front:
- // nums.unshift(45)
- // console.log(nums)
- // // Take off from end:
- // nums.pop()
- // console.log(nums)
- // // Take off from front:
- // nums.shift()
- // console.log(nums)
- // // Splice values:
- // let miniNums = nums.splice(1, 1, 6, 7, 8)
- // console.log(miniNums + '\n' + nums)
- // // Reverse:
- // nums.reverse()
- // console.log(nums)
- // // Concatenate array:
- // let newNums = nums.concat(4, 11)
- // console.log(newNums)
- // // ------Sorting arrays------
- // // string array, sorts by alpha:
- // strings.sort()
- // console.log(strings)
- // strings.reverse()
- // console.log(strings)
- // // num array, sorts by first number:
- // nums.sort()
- // console.log(nums)
- // // use the "compare function" for least to greatest:
- // nums.sort((x, y) => {
- // return x - y
- // })
- // console.log(nums)
- // // use the "compare function" for greatest to least:
- // nums.sort((x, y) => {
- // return y - x
- // })
- // console.log(nums)
- // // Find: find the 1st number under 50
- // function under50 (num) {
- // return num < 50
- // }
- // console.log(nums.find(under50))
- // // Find: find the 1st number over 50
- // nums.push(79)
- // function over50 (num) {
- // return num > 50
- // }
- // console.log(nums.find(over50))
- // Object Literals *****************************************************************
- // // Create an object literal containing the following property-types: string, number, array, abject, function
- // let person = {
- // firstName: 'Rob',
- // LastName: 'Love',
- // age: '37',
- // interests: ['sports', 'motorcycles', 'carpentry'],
- // address: {
- // city: 'Chicago',
- // state: 'IL'
- // },
- // sayName: function () {
- // return `Hi, my name is ${this.firstName}`
- // }
- // }
- // console.log(person)
- // // Get a specific value from each property using dot-notation. give an example of bracket-notation:
- // console.log(person.LastName)
- // console.log(person.age)
- // console.log(person['firstName'])
- // console.log(person.interests)
- // console.log(person.interests[1])
- // console.log(person.address)
- // console.log(person.address.city)
- // console.log(person.sayName())
- // console.log(person['interests'][[2]])
- // // Create a method on the object that uses the this keyword:
- // person.sayAge = function () {
- // console.log(`I am ${this.age} years old`)
- // }
- // person.sayAge()
- // // Create an array of object literals:
- // let team = [{name: 'Jerry', position: 'Manager'}, {name: 'Rena', position: 'clerk'}, {name: 'Ron', position: 'clerk'}]
- // console.log(team)
- // Dates and Times ******************************************************************
- // If Statements and Comparison operators *******************************************
- // // Create example if, if/else, and else if statements with the following...
- // // Equal To: ==
- // let one = 1
- // if (one == true) {
- // console.log('this is true')
- // }
- // // Not Equal To: !=
- // if (one != true) {
- // console.log('this is true')
- // } else {
- // console.log('this is not true')
- // }
- // // Equal to value and Type: ===
- // let one2 = '1'
- // if (one === one2) {
- // console.log(`${one} is equal to ${one2} in both value and type`)
- // } else {
- // console.log(`one, value:${one} type:${typeof one}`)
- // console.log(`one2, value:${one2} type:${typeof one2}`)
- // }
- // // Not Equal to value and Type: !==
- // let word = 'big'
- // let word2 = 'big'
- // if (typeof word !== typeof word2) {
- // console.log('the variables are not equal in type')
- // } else {
- // console.log('the variables are equal in both value and type')
- // }
- // // Check to see if variable undefined: typeof varName !== 'undefined'
- // const person = undefined
- // if (person !== undefined) {
- // console.log('the variable is not equal to undefined')
- // } else {
- // console.log('they are equal')
- // }
- // // Greater or Less than:
- // if (57 < 33) {
- // console.log('57 is less than 33')
- // } else {
- // console.log('57 is greater than 33')
- // }
- // // Else if:
- // let myFavCar = 'gmc'
- // let car1 = 'ford'
- // let car2 = 'honda'
- // let car3 = 'gmc'
- // if (car1 === myFavCar) {
- // console.log(`${car1} is the car for me`)
- // } else if (car2 === myFavCar) {
- // console.log(`${car2} is the car for me`)
- // } else if (car3 === myFavCar) {
- // console.log(`${car3} is the car for me`)
- // }
- // // Logical Operators:
- // // AND &&
- // if (car3 === myFavCar && car1 !== myFavCar) {
- // console.log('that\'s right')
- // }
- // // OR ||
- // if (car1 === car2 || car2 === car3) {
- // console.log('one of these statements is true')
- // } else {
- // console.log('both of these statements are false')
- // }
- // // Shorthand:
- // // TERNARY OPERATOR: ? (if), : (else)
- // let scoreOne = 99
- // let scoreTwo = 79
- // scoreOne > scoreTwo ? console.log('scoreOne!') : console.log('scoreTwo!')
- // // if/else Without Braces:
- // if (scoreOne === scoreTwo)
- // console.log('Tie')
- // else
- // console.log('We have a winner')
- // // Switch Statements ******************************************************************
- // // Create a switch statement with several cases:
- // let day = ['Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday']
- // switch (day[2]) {
- // case 'Monday':
- // console.log('work @ 7am')
- // break
- // case 'Tuesday':
- // console.log('work @ 8am')
- // break
- // case 'Wednesday':
- // console.log('work @ 9am')
- // break
- // }
- // // Functions, function Declarations and function Expressions **************************
- // // Function Declarations example:
- // function Callme () {
- // return 'Hello there, what can I do for you?'
- // }
- // console.log(Callme())
- // // function with parameters & multiple parameters:
- // function double (val) {
- // if (typeof val === typeof 'string') {
- // return val.append(' ' + val)
- // } else if (typeof val === typeof 5) {
- // return val * 2
- // } else {
- // return 'I can\'t handle this type'
- // }
- // }
- // console.log(double(8))
- // // default values for parameters example:
- // const fullName = (first = 'John', last = 'Doe') => {
- // return `Congratulations, your full name is ${first} ${last}!`
- // }
- // console.log(fullName('Ben', 'Faught'))
- // // function expression example:
- // const hello = function () {
- // console.log('hello world!')
- // }
- // hello()
- // // named function expression:
- // const multiply = function multiply (num, multiplier) {
- // return num * multiplier
- // }
- // console.log(multiply(7, 3))
- // // Immediately Invoked Function Expressions - IIFEs:
- // (function () {
- // console.log('I am an IIFE :)')
- // })();
- // // IIFE with params:
- // (function (name) {
- // console.log('I am an IIFE with params, my name is ' + name)
- // })('Biffie');
- // // TRUE or False, in modules, IIFEs can provide private methods and properties, by keeping everything scoped to that module? true
- // // Property Methods... Create a method within an object:
- // let myObj = {
- // name: 'Larry',
- // age: 30,
- // iam: function () {
- // console.log(`my name is ${this.name} and I am ${this.age} years old.`)
- // }
- // }
- // myObj.iam()
- // // Create a method on an object from outside the object:
- // myObj.hello = function () {
- // console.log(`this is ${this.name}, just saying hello!`)
- // }
- // myObj.hello()
- // General Loops ************************************************************************
- // // create a general for loop:
- // for (let i = 0; i < 5; i++) {
- // console.log('the count is: ' + i)
- // }
- // // for loop with a condition inside that uses the continue keyword:
- // for (let i = 0; i < 15; i++) {
- // if (i >= 5 && i < 10) {
- // console.log('continue: ' + i)
- // continue
- // }
- // console.log('the count is: ' + i)
- // }
- // // for loop with a condition inside that uses the break keyword:
- // for (let i = 0; i < 10; i++) {
- // if (i === 6) {
- // console.log('I\'m leaving this loop at 6')
- // break
- // }
- // console.log('looping @: ' + i)
- // }
- // // create a while loop:
- // let m = 0
- // while (m <= 3) {
- // console.log('value is: ' + m)
- // m++
- // }
- // // true or false, a do-while loop will run it's first iteration regardless of the conditional. true
- // // create a do while loop:
- // do {
- // console.log('hello')
- // m++
- // } while (m < 1)
- // // use a for loop to iterate through an array: hint: array.length
- // let list = ['eggs', 'milk', 'bread', 'bologna']
- // for (let i = 0; i < list.length; i++) {
- // console.log(list[i])
- // }
- // // use forEach() to loop through an array:
- // const users = [
- // {id: '7', first: 'Tom', last: 'Brady'},
- // {id: '8', first: 'Mary', last: 'Smith'},
- // {id: '9', first: 'Jake', last: 'Paul'}
- // ]
- // users.forEach(function (user) {
- // console.log(user.last)
- // console.log(user)
- // })
- // // use forEach() to loop through an array, using the index & array keyword as a parameter in the callback:
- // users.forEach(function (user, index, array) {
- // console.log(user.first)
- // console.log(index)
- // console.log(array)
- // })
- // // use map() to loop through an existing array of objects, and create an new array from one of the properties of that object:
- // const ids = users.map(function (user) {
- // return user.id
- // })
- // console.log(ids)
- // // create a for-in loop on an object literal (print out both the key and value):
- // const person = {
- // name: 'Bob',
- // age: 'White',
- // dob: '11-3-1977',
- // city: 'New York'
- // }
- // for (let x in person) {
- // console.log(x)
- // console.log(person[x])
- // console.log(`${x}: ${person[x]}`)
- // }
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