Quiz - YDKJS: Up & Going 2/3

Chapter 2: Into JavaScript

Self-Evaluation

Section: Values & Types

1. Name the 7 built-in types available in JavaScript.

2. Name the two ways to access object properties.

3. Typeof. Look at the following snippets and write what would be the ouput.

Snippet #1

console.log(typeof a);
var a;

Snippet #2

console.log(typeof "hello world");

Snippet #3

console.log(typeof false);

Snippet #4

console.log(typeof 21);

Snippet #5

console.log(typeof null);

Snippet #6

console.log(typeof undefined);

Snippet #7

console.log(typeof { name: "John" });

Snippet #8

console.log(typeof typeof 42);

Snippet #9

console.log(typeof 3.1416);

Snippet #10

console.log(typeof "10");

Snippet #11

var person = {
  name: "Peter",
  age: 40
};

console.log(typeof person.name);
console.log(typeof person.age);
console.log(typeof person.lastName);

Snippet #12

console.log(typeof []);

Snippet #13

console.log(typeof ["Hello", 20, true][2]);

Snippet #14

console.log(typeof ["Hello", 20, true][3]);

Snippet #15

console.log(typeof { a: 2 }["a"]);

Snippet #16

var index = "c";
console.log({ a: 1, b: 2, c: 3 }[index]);

Snippet #17

console.log({ x: 100, y: 200 }.x);

Snippet #18

function getX (point) {
  return point.x;
}

getX.PI = '3.1416';

console.log(typeof getX);
console.log(typeof getX({ x: 34, y: 54 }));
console.log(typeof getX.PI);

Snippet #19

var n = "47";
console.log(typeof n);
console.log(typeof Number(n));

Snippet #20

var n = "47";
console.log(typeof (n * 2));

4. Coercion. Label the following code snippets with `explicit` or `implicit` accordingly.

Snippet #21

var a = "13";
var b = a * 2;
console.log(a); // "13"
console.log(b); // 26

Snippet #22

var a = "13";
var b = Number(a);
console.log(a); // "13"
console.log(b); // 13

5. List the `falsy` values in JS.

6. Boolean Coercion. Write the result `true` or `false` for the following snippets.

Snippet #23

Boolean('');

Snippet #24

Boolean('.');

Snippet #25

Boolean("");

Snippet #26

Boolean(0);

Snippet #26-2

Boolean("0");

Snippet #27

Boolean(1);

Snippet #28

Boolean(1/0);

Snippet #29

Boolean(0/1);

Snippet #30

Boolean(NaN);

Snippet #31

Boolean(Infinity);

Snippet #32

Boolean(0 + "0");

Snippet #33

Boolean("0" + 0);

Snippet #34

Boolean("0" * 1);

Snippet #35

Boolean(1 * "0");

Snippet #36

Boolean(-1 * 0);

Snippet #37

Boolean(null);

Snippet #38

Boolean(undefined);

Snippet #39

Boolean(false);

Snippet #40

Boolean(true);

Snippet #41

Boolean([]);

Snippet #42

Boolean([1, 2, 3]);

Snippet #43

Boolean([0].toString());

Snippet #43-2

Boolean([1, '', {}][1]);

Snippet #43-3

Boolean([1, '', { n: 0 }][2].n);

Snippet #44

Boolean([].toString());

Snippet #45

Boolean({});

Snippet #45-2

Boolean({}.toString());

Snippet #46

Boolean({ name: "Doe" });

Snippet #47

Boolean({ toString: function () {
  return '';
}}.toString());

Snippet #48

Boolean({ number: 0 }.number);

Snippet #49

Boolean({ char: 'a' }.char);

Snippet #50

Boolean(function noop() {});

7. Operator that checks for value equality with coercion allowed:

8. Operator that checks for value equality without allowing coercion:

9. Operator that checks for value non-equality with coercion allowed:

10. Operator that checks for value non-equality without allowing coercion:

11. Equality Coercion. Write the result `true` or `false` for the following snippets:

Snippet #51

"12" == 12;

Snippet #51-2

12 === "12";

Snippet #52

1 == true;

Snippet #52-2

true === 1;

Snippet #53

false == 0;

Snippet #54

false == "false";

Snippet #55

"" == false;

Snippet #56

null == false;

Snippet #57

undefined == null;

Snippet #58

false == undefined;

Snippet #59

0 == "";

Snippet #60

0 == null;

Snippet #61

var a;
a == null;

Snippet #62

({} == {});

Snippet #63

({} === {});

Snippet #64

 [] == [];

Snippet #65

 [1, 2, 3] === [1, 2, 3];

Snippet #66

 [1, 2, 3] == "1,2,3";

Snippet #67

 NaN == NaN;

Snippet #68

 NaN === NaN;

Snippet #68-2

 (function noop (){}) == (function noop (){});

Snippet #68-3

 (function noop (){}).toString() == (function noop (){});

12. Inequality Coercion. Write `true` or `false` for the following snippets

Snippet #69

 2 > "1";

Snippet #70

 "a" < "b";

Snippet #71

 3 < "a";

Snippet #72

 "3" < "a";

Snippet #73

 0 > NaN;

Variables

13. Are these valid JS indentifiers? Fill the table with `true` or `false`

identifier	is valid?
`Name`	your answer here
`0duck`	your answer here
`last.name`	your answer here
`$account`	your answer here
`_age`	your answer here
`-price`	your answer here
`car[123]`	your answer here
`for`	your answer here

14. What's hoisting?

15. Hoisting. What would be the output for this snippet?

Snippet #74

a = 10;

foo ();

function foo () {
  a = 5;

  console.log(a);

  var a;
}

var a;

console.log(a);

16. What's the main difference between `var` and `let`?

17. Nested Scopes, `var` & `let`. Write the output for the following code snippets

Snippet #75

var a = 1;

function foo () {
  if (a == 1) {
    var b = 2;
  }

  console.log(b);
}

foo();

Snippet #76

var a = 1;

function foo () {
  if (a == 1) {
    let b = 2;
  }

  console.log(b);
}

foo();

Snippet #77

function foo () {
  var a = 10
}

foo();

console.log(a);

Snippet #78

function foo () {
  a = 20
}

foo();

console.log(a);

Section: Conditionals

18. Write the code to log if a number is `even` or `odd` using the `if` statement, `switch` statement and the conditional operator `?:` aka ternay operator

Clue: you can determine if a number is even if the remainder of n divided by 2 is equal to 0. Use the remainder operator %.

if Solution:

// your code here

switch Solution:

// your code here

ternary Solution:

// your code here

Section: Strict Mode

19. In your own words, what's `use strict;`?

20. Use Strict. Write the output for the following code snippets

Snippet #79

function yummy () {
  a = 50
}

yummy();

console.log(a);

Snippet #80

'use strict';

function yummy () {
  a = 50
}

yummy();

console.log(a);

Section: Functions As Values

21. Complete the sentence

Functions are the primary mechanism of _____ in JS.

22. Create a function `square` that takes one parameter `number` that returns the result of that `number` multiplied by itself. You need to perform this in `3` different ways

22.1. by using `function declaration` syntax.

Solution:

// your code here

22.2. by using `function expression with an anonymous function` syntax.

Solution:

// your code here

22.3 by using `function expression with a named function` syntax.

Solution:

// your code here

23. What's an `IIFE`? Give an example.

// your code here

24. What's a `closure` in JS?

25. Closure. What would be the output for the following code?

Snippet #81

function createHello (greeting) {
  return function greet (name) {
    return greeting + " " + name + "!";
  }
}

var greetInSpanish = createHello('Hola');

console.log(greetInSpanish("Pedro"));
console.log(createHello('Hi')("Mike"));

Section: `this` Keyword

26. `this`. Write the output for the following code

Snippet #82

// Kitties
function sayHello() {
  console.log("Hello " + this.name);
}

var name = "Fluffy";

sayHello();

var kitty = {
  name: "Buttercup",
  sayHello: sayHello
};

kitty.sayHello();

sayHello.call({ name: "Cocoa" });

new sayHello();

Section: Prototypes

27. Prototypes. Write the output for the following code

Snippet #83

var animal = {
  walk: "I'm walking!"
};

var bird = Object.create(animal);

bird.fly = "I'm flying!";

var penguin = Object.create(bird);

penguin.fly = "I can't fly :(";
penguin.swim = "I'm swimming!";

var canary = Object.create(bird);

var tiger = Object.create(animal);

console.log(tiger.walk);
console.log(tiger.fly);
console.log(canary.fly);
console.log(canary.walk);
console.log(canary.swim);
console.log(penguin.fly);
console.log(penguin.walk);
console.log(penguin.swim);

Section: Old & New

28. What are the two main techniques to make older browsers work with newer features available in JS? Describe each

Section: Non-JavaScript

29. Is the `alert` method provided by the JS engine?

Section: Challenges

2.1 Create a module in an `IIFE` stored in a variable `calculator` that exposes 4 methods: `plus`, `minus`, `times` and `dividedBy`. Each method should receive one parameter `firstNumber` and return a function that receives another parameter `secondNumber`. Every method should perform the operation it describes, for example, it's expected that `plus` adds the `firstNumber` to the `secondNumber`, `dividedBy` should divide the `secondNumber` by the `firstNumber` and so on. The idea is to have "stored" the `firstNumber` to perform the next operations with it.

TIP: You can create a script.jsfile and test your code in the browser or node.js.

Solution:

// create your calculator module here
var calculator;

// Do NOT touch this code
const testCases = [
  { type: "plus", n1: 3, n2: [1, 2, 3], expected: [4, 5, 6] },
  { type: "minus", n1: 1, n2: [1, 0, -1], expected: [0, -1, -2] },
  { type: "times", n1: 5, n2: [2, 5, 10], expected: [10, 25, 50] },
  { type: "dividedBy", n1: 10, n2: [10, 100, 1000], expected: [1, 10, 100] }
];

const result = testCases.every(test => {
  const operation = calculator[test.type](test.n1);
  return test.n2.every((number, i) => {
    const testPassed = operation(number) === test.expected[i];
    if (!testPassed) {
      console.log(`Expected: ${operation(number)} to be: ${test.expected[i]}. Operation: secondNumber(${number}) ${test.type} firstNumber(${test.n1})`);
    }
    return testPassed;
  });
});

console.log("All tests passed: ", result);

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Quiz - YDKJS: Up & Going 2/3

Chapter 2: Into JavaScript

Self-Evaluation

Section: Values & Types

1. Name the 7 built-in types available in JavaScript.

2. Name the two ways to access object properties.

3. Typeof. Look at the following snippets and write what would be the ouput.

Snippet #1

Snippet #2

Snippet #3

Snippet #4

Snippet #5

Snippet #6

Snippet #7

Snippet #8

Snippet #9

Snippet #10

Snippet #11

Snippet #12

Snippet #13

Snippet #14

Snippet #15

Snippet #16

Snippet #17

Snippet #18

Snippet #19

Snippet #20

4. Coercion. Label the following code snippets with explicit or implicit accordingly.

Snippet #21

Snippet #22

5. List the falsy values in JS.

6. Boolean Coercion. Write the result true or false for the following snippets.

Snippet #23

Snippet #24

Snippet #25

Snippet #26

Snippet #26-2

Snippet #27

Snippet #28

Snippet #29

Snippet #30

Snippet #31

Snippet #32

Snippet #33

Snippet #34

Snippet #35

Snippet #36

Snippet #37

Snippet #38

Snippet #39

Snippet #40

Snippet #41

Snippet #42

Snippet #43

Snippet #43-2

Snippet #43-3

Snippet #44

Snippet #45

Snippet #45-2

Snippet #46

Snippet #47

Snippet #48

Snippet #49

Snippet #50

7. Operator that checks for value equality with coercion allowed:

8. Operator that checks for value equality without allowing coercion:

9. Operator that checks for value non-equality with coercion allowed:

10. Operator that checks for value non-equality without allowing coercion:

11. Equality Coercion. Write the result true or false for the following snippets:

Snippet #51

Snippet #51-2

Snippet #52

Snippet #52-2

Snippet #53

4. Coercion. Label the following code snippets with `explicit` or `implicit` accordingly.

5. List the `falsy` values in JS.

6. Boolean Coercion. Write the result `true` or `false` for the following snippets.

11. Equality Coercion. Write the result `true` or `false` for the following snippets:

12. Inequality Coercion. Write `true` or `false` for the following snippets

13. Are these valid JS indentifiers? Fill the table with `true` or `false`

16. What's the main difference between `var` and `let`?

17. Nested Scopes, `var` & `let`. Write the output for the following code snippets

18. Write the code to log if a number is `even` or `odd` using the `if` statement, `switch` statement and the conditional operator `?:` aka ternay operator

19. In your own words, what's `use strict;`?

22. Create a function `square` that takes one parameter `number` that returns the result of that `number` multiplied by itself. You need to perform this in `3` different ways

22.1. by using `function declaration` syntax.

22.2. by using `function expression with an anonymous function` syntax.

22.3 by using `function expression with a named function` syntax.

23. What's an `IIFE`? Give an example.

24. What's a `closure` in JS?

Section: `this` Keyword

26. `this`. Write the output for the following code

29. Is the `alert` method provided by the JS engine?