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NW Class 5 - Mohammed Alhallaq- Javascript - Core1-Week3 #138

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NW Class 5 - Mohammed Alhallaq- Javascript - Core1-Week3 #138

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a314c00
solve exercises
mhallaq Sep 22, 2022
01cd968
solve mandatory
mhallaq Sep 22, 2022
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13 changes: 8 additions & 5 deletions 1-exercises/A-undefined/exercise.js
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Expand Up @@ -12,25 +12,28 @@
// Example 1
let a;
console.log(a);

// this is undefined because it's null , ( contains no value )

@yogaraptor yogaraptor Sep 27, 2022

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Actually, it's undefined, not null. For something to be null we have to explicitly mark it as such, like this:

let a = null;

You would use null when you want to intentionally mark something as empty/missing, e.g. in this list, the singer Cher has no last name - this isn't a mistake, it's just a fact of her name:

const artists = [
  {
    firstName: 'Ravi',
    lastName: 'Shankar',
    numberOfSongs: 93
  },
  {
    firstName: 'Cher',
    lastName: null,
    numberOfSongs: 72    
  },
  {
    firstName: 'Miles',
    lastName: 'Davis',
    numberOfSongs: 89
  }
]

@mhallaq mhallaq Sep 27, 2022

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Thanks Tom for this clear elaborated explaination. :-)


// Example 2
function sayHello() {
let message = "Hello";
let message = "Hello";
}

let hello = sayHello();
console.log(hello);

// this function return undefined after run because there is no return statement in the function.

// Example 3
function sayHelloToUser(user) {
console.log(`Hello ${user}`);
console.log(`Hello ${user}`);
}

sayHelloToUser();

// this function also does not have a return statement in it , thats why it return undefined

// Example 4
let arr = [1,2,3];
let arr = [1, 2, 3];
console.log(arr[3]);

// this array contains only elements for the indecies 0,1,2 , but the value of the index 3 is not yet defined, null. that's why it returns undefined.
16 changes: 12 additions & 4 deletions 1-exercises/B-while-loop/exercise.js
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*/

function evenNumbers(n) {
// TODO
// TODO
let iterationNumber = 0;
let resultEvenNumbers = "";
while (iterationNumber < n) {
resultEvenNumbers = resultEvenNumbers.concat(iterationNumber * 2, ",");
iterationNumber++;
}

return resultEvenNumbers;
}

evenNumbers(3); // should output 0,2,4
evenNumbers(0); // should output nothing
evenNumbers(10); // should output 0,2,4,6,8,10,12,14,16,18
console.log(evenNumbers(3)); // should output 0,2,4
console.log(evenNumbers(10)); // should output 0,2,4,6,8,10,12,14,16,18
console.log(evenNumbers(0)); // should output nothing
28 changes: 18 additions & 10 deletions 1-exercises/C-while-loop-with-array/exercise.js
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*/

const BIRTHDAYS = [
"January 7th",
"February 12th",
"April 3rd",
"April 5th",
"May 3rd",
"July 11th",
"July 17th",
"September 28th",
"November 15th"
"January 7th",
"February 12th",
"April 3rd",
"April 5th",
"May 3rd",
"July 11th",
"July 17th",
"September 28th",
"November 15th",
];

function findFirstJulyBDay(birthdays) {
// TODO
// TODO
let i = 0;
while (i < BIRTHDAYS.length) {
if (BIRTHDAYS[i].includes("July")) {
return BIRTHDAYS[i];
}
i++;
}
return 0;
}

console.log(findFirstJulyBDay(BIRTHDAYS)); // should output "July 11th"
12 changes: 10 additions & 2 deletions 1-exercises/D-do-while/exercise.js
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*/

function evenNumbersSum(n) {
// TODO
// TODO
let count = 0;
let sum = 0;
do {
if (!(count % 2)) sum = sum + count;

@yogaraptor yogaraptor Sep 27, 2022

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Modulus. Nice 😁

count+=2;
} while (count < n * 2);

return sum;
}

console.log(evenNumbersSum(3)); // should output 6
console.log(evenNumbersSum(0)); // should output 0
console.log(evenNumbersSum(10)); // should output 90
console.log(evenNumbersSum(10)); // should output 90
7 changes: 2 additions & 5 deletions 1-exercises/E-for-loop/exercise1.js
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Change the while loop below into a for loop.
*/


// Change the below code to use a for loop instead of a while loop.
let i = 0;
while(i < 26) {
console.log(String.fromCharCode(97 + i));
i++;
for (let i = 0; i < 26; i++) {
console.log(String.fromCharCode(97 + i));
}
// The output shouldn't change.
23 changes: 10 additions & 13 deletions 1-exercises/E-for-loop/exercise2.js
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*/

const WRITERS = [
"Virginia Woolf",
"Zadie Smith",
"Jane Austen",
"Bell Hooks",
"Yukiko Motoya"
]

const AGES = [
59,
40,
41,
63,
49
"Virginia Woolf",
"Zadie Smith",
"Jane Austen",
"Bell Hooks",
"Yukiko Motoya",
];

const AGES = [59, 40, 41, 63, 49];

// TODO - Write for loop code here

for (i = 0; i < WRITERS.length; i++) {
console.log(`${WRITERS[i]} is ${AGES[i]} years old`);
}
/*
The output should look something like this:

Expand Down
13 changes: 8 additions & 5 deletions 1-exercises/F-for-of-loop/exercise.js
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// TODO Use a for-of loop to output each of the tube stations below.
let tubeStations = [
"Aldgate",
"Baker Street",
"Picadilly Circus",
"Oxford Street",
"Tottenham Court Road"
"Aldgate",
"Baker Street",
"Picadilly Circus",
"Oxford Street",
"Tottenham Court Road",
];

for (let i = 0; i < tubeStations.length; i++) console.log(tubeStations[i]);

// TODO Use a for-of loop to capitalise and output each letter in the string seperately.
let str = "codeyourfuture";
let letter;
for (let letter of str) console.log(letter.toUpperCase());
100 changes: 65 additions & 35 deletions 2-mandatory/1-weather-report.js
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- Hint: you can call the temperatureService function from your function
*/

function getTemperatureReport(cities) {
// TODO
let cities = [
"London",
"Paris",
"Barcelona",
"Dubai",
"Mumbai",
"São Paulo",
"Lagos",
];
let citiesTemp = [
"London",
10,
"Paris",
12,
"Barcelona",
17,
"Dubai",
27,
"Mumbai",
29,
"São Paulo",
23,
"Lagos",
33,
];

function getTempratur(city) {
let index = citiesTemp.indexOf(city);
index++;
return citiesTemp[index];
}
Comment on lines +14 to 44

@yogaraptor yogaraptor Sep 27, 2022

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This is an interesting approach! I think in some lower-level programming languages, storing info like this (an array with alternating keys and values) might be more common place. In JS, it's more conventional to use a dictionary:

const cityTemperatures = {
    "São Paulo":  23,
  "Lagos":  33
}

or a Map as used by the function the exercise provides below (the exercise suggested you use that function rather than write your own, but nothing wrong with trying things out for yourself 💪 )


function getTemperatureReport(cities) {
let tempratureReport = [];
// TODO
for (let i = 0; i < cities.length; i++) {

@yogaraptor yogaraptor Sep 27, 2022

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Because you don't need the index (i) for your output here, you could use a for of loop instead.

@mhallaq mhallaq Sep 27, 2022

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I agree, thank you.

let temp = getTempratur(cities[i]);
tempratureReport[i] = `The temperature in ${cities[i]} is ${temp} degrees`;
}
return tempratureReport;
}

/* ======= TESTS - DO NOT MODIFY ===== */

function temperatureService(city) {
let temparatureMap = new Map();

temparatureMap.set('London', 10);
temparatureMap.set('Paris', 12);
temparatureMap.set('Barcelona', 17);
temparatureMap.set('Dubai', 27);
temparatureMap.set('Mumbai', 29);
temparatureMap.set('São Paulo', 23);
temparatureMap.set('Lagos', 33);
return temparatureMap.get(city);
let temparatureMap = new Map();

temparatureMap.set("London", 10);
temparatureMap.set("Paris", 12);
temparatureMap.set("Barcelona", 17);
temparatureMap.set("Dubai", 27);
temparatureMap.set("Mumbai", 29);
temparatureMap.set("São Paulo", 23);
temparatureMap.set("Lagos", 33);

return temparatureMap.get(city);
}

test("should return a temperature report for the user's cities", () => {
let usersCities = [
"London",
"Paris",
"São Paulo"
]

expect(getTemperatureReport(usersCities)).toEqual([
"The temperature in London is 10 degrees",
"The temperature in Paris is 12 degrees",
"The temperature in São Paulo is 23 degrees"
]);
let usersCities = ["London", "Paris", "São Paulo"];

expect(getTemperatureReport(usersCities)).toEqual([
"The temperature in London is 10 degrees",
"The temperature in Paris is 12 degrees",
"The temperature in São Paulo is 23 degrees",
]);
});

test("should return a temperature report for the user's cities (alternate input)", () => {
let usersCities = [
"Barcelona",
"Dubai"
]

expect(getTemperatureReport(usersCities)).toEqual([
"The temperature in Barcelona is 17 degrees",
"The temperature in Dubai is 27 degrees"
]);
let usersCities = ["Barcelona", "Dubai"];

expect(getTemperatureReport(usersCities)).toEqual([
"The temperature in Barcelona is 17 degrees",
"The temperature in Dubai is 27 degrees",
]);
});

test("should return an empty array if the user hasn't selected any cities", () => {
expect(getTemperatureReport([])).toEqual([]);
});
expect(getTemperatureReport([])).toEqual([]);
});
21 changes: 13 additions & 8 deletions 2-mandatory/2-retrying-random-numbers.js
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// This function shouldn't be changed
function generateRandomNumber() {
console.log("Generating number...");
return Math.round(Math.random() * 100);
console.log("Generating number...");
return Math.round(Math.random() * 100);
}

function getRandomNumberGreaterThan50() {
// TODO - implement using a do-while loop
// TODO - implement using a do-while loop
let randomNumber;

@yogaraptor yogaraptor Sep 27, 2022

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Nice. Simple and concise 👌

do {
randomNumber = generateRandomNumber();
} while (randomNumber <= 50);
return randomNumber;
}

/* ======= TESTS - DO NOT MODIFY ===== */

test("Returned value should always be greater than 50", () => {
expect(getRandomNumberGreaterThan50()).toBeGreaterThan(50);
expect(getRandomNumberGreaterThan50()).toBeGreaterThan(50);
expect(getRandomNumberGreaterThan50()).toBeGreaterThan(50);
expect(getRandomNumberGreaterThan50()).toBeGreaterThan(50);
expect(getRandomNumberGreaterThan50()).toBeGreaterThan(50);
expect(getRandomNumberGreaterThan50()).toBeGreaterThan(50);
expect(getRandomNumberGreaterThan50()).toBeGreaterThan(50);
expect(getRandomNumberGreaterThan50()).toBeGreaterThan(50);
expect(getRandomNumberGreaterThan50()).toBeGreaterThan(50);
expect(getRandomNumberGreaterThan50()).toBeGreaterThan(50);
});
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