SolutionsIntroductionToJs.md

Introduction to JavaScript

Solutions are also available as notebook

Variables & Datatypes

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Exercise 1 a) Create three variables and assign values with different data types to them

    // number, string, boolean
    let number = 10
    let name = "Rikku"
    let likesProgramming = true

Exercise 1 b) Print all the variables using JavaScript's built-in function console.log()

    console.log(number, name, likesProgramming)

Exercise 1 c) Print the data type of each variable using JavaScript's built-in keyword "typeof"

    console.log(typeof number)

    console.log(typeof name)

    console.log(typeof likesProgramming)

Exercise 2 How do we use variables? Explore with arithmetic operators (+, -, *, /)!

    // Example
    let firstValue = 3
    let secondValue = 5

    let result = firstValue + secondValue

    result = firstValue - secondValue

    result = firstValue * secondValue

    result = firstValue / secondValue

Arrays

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    // Example
    let veggies = ['orange', 'lime', 'olive', 'tomato', 'plum', 'maroon']

    veggies[0]

    veggies[1]

We can pick one or more from the start, and get a new array of the rest

    let [firstVeggie, ...otherVeggies] = veggies

    console.log(firstVeggie)

We can also create a slice of the array, specifying where to start and end

    veggies.slice(2, 5)

    veggies.slice(2)

    veggies.slice(0, 2)

Exercise 3 a) Create an array with names of your friends and print the name of the first, second and then the rest

    let names = ["Tusse", "Misse", "Nisse", "Lusse"]

    names[0]

    names[1]

    let [,, ...rest] = names

    console.log(rest)

Exercise 3 b) Log your array of names using different slices

    names.slice(0,2)

    names.slice(2)

    names.slice(1, 3)

Exercise 4 a) Count how many names you have added to the a array using array.length

    names.length

Exercise 4 b) Change the array, adding a new name first: array = [newItem, ...array]

    names = ['Hubbe' , ...names]

Exercise 4 c) Change the array, removing two names: [first, second, ...array] = array

    [katt1, katt2, ...names] = names

Log the removed names. Does it look as expected?

    console.log(katt1, katt2)

Exercise 4 d) Remove two names like above, and then ignore them: [, , ...array] = array

    [, , ...names] = names

Log the array. Does it look as expected?

    console.log(names)

Exercise 4 e) Combine two arrays of names, using: [...firstArray, ...secondArray]

    let moreNames = ["Murre", "Miso", "Tasse"]
    names = [...names, ...moreNames]

Log the array. Does it look as expected?

    console.log(names)

For-loops

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    // Example
    for (let veggie of veggies) {
        console.log(veggie)
    }

    for (let index in veggies) {
        veggies[index] = veggies[index] + 's'
    }
    console.log(veggies)

Exercise 5 a) Log each name in your array of names

    for (let name of names) {
        console.log(name)
    }

Exercise 5 b) Add a small change to each name in your array

    for (let index in names) {
        names[index] = names[index] + 's'
    }
    console.log(names)

Objects

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    // Example
    let countries = { "sweden" : "stockholm", "great britain" : "london", "japan" : "tokyo" }

    let capital = countries["sweden"]

Exercise 6 a) Get the capital of Great Britain and Japan using the object "countries"

    countries["great britain"]

    countries.japan

Exercise 6 b) Add a new key-value pair to the object "countries"

    countries.taiwan = 'taipei'

Exercise 6 c) Update Sweden's capital to Umeå

    countries.sweden = 'umeå'

Exercise 6 d) Remove the key-value pair Sweden-Stockholm from the object

    delete countries.sweden

Log the object. Does it look as expected?

    console.log(countries)

Exercise 6 e) Print each key-value pair in the object countries

    for (let [key, value] of Object.entries(countries)) {
        console.log("Country: "+key+", Capital: "+value)
    }

Functions

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    // Example
    function myFunction (param1, param2) {
        // Block of code
    }
    (param1, param2) => {
        // Block of code
    }
    // log the name and content
    console.log(myFunction.name)
    console.log(myFunction.toString())

    // arrow functions are anonymous until you assign them to a variable
    let arrowFunction = () => {}
    arrowFunction.name

We will start with creating a function that can add two numbers.

    function addTwoNumbers (number1, number2) {
    let result = number1 + number2
    return result
    }

Let's try to use it!

    addTwoNumbers(1, 2)

    addTwoNumbers(5, 20)

Exercise 7 a) Create a function that can calculate the difference between two numbers

    function subtract(number1, number2) {
        let result = number1 - number2
        return result
    }

Exercise 7 b) Use the function. Does it return the expected results?

    subtract(5, 20)

Exercise 7 c) Create a function that can multiply two numbers

    function multiply(number1, number2) {
        result = number1 * number2
        return result
    }

Exercise 7 d) Use the function. Does it return the expected results?

    multiply(5, 20)

Exercise 7 e) Create a function that can divide two numbers

    function divide(number1, number2) {
        result = number1 / number2
        return result
    }

Exercise 7 f) Use the function. Does it return the expected results?

    divide(5, 20)