JavaScript fundamentals - exercices

Given the following code:

1
2
3
let s = "Hello";
let x = s.toLowerCase();
let l = s.length;

1. What are the types of the following:

1. s
2. x
3. s.toLowerCase()
4. s.toLowerCase
5. s.length
6. l

2. In let x = 5 + 6;, what is +?

1. Function
2. Operator
3. Number
4. Aggregator

3. In let x = 5 + 6;, what is let?

1. Variable
2. Keyword
3. Operator
4. Constant

Given the following code:

1
let x = z[y];

4. What is y?

1. Index
2. Key
3. Index or key
4. Array

Given the following code:

1
2
3
let y = 1;
let x = [1, 2, 3];
let z = x[y];

5. What is y?

1. Index
2. Key
3. Index or key
4. Array

Given the following code:

1
2
3
4
5
6
let joe = {
  name: 'Joe',
  age: 24
};
let joesName = joe.name;
let joesAge = joe['age'];

6. What is 'age' in the last line?

1. Index
2. Key
3. Array
4. Object

7. What are name and age of the object joe?

1. Index
2. Key
3. Object
4. Property

Given the following code:

1
2
3
let y = 'length';
let x = [1, 2, 3];
let z = x[y];

7. What is y

1. Index
2. Key
3. Index or key
4. Array

8. What is the element for index 1 in array x?

9. Fill in: "The value of the (...) length of x is (...)"

10. What is the name of these functions?

1. function a() { return true; }
2. let a = function b() { return true; }
3. let c = function () { return true; }

11. Write a function that has two parameters called first and second

12. Write a function call that passes three arguments.

13. Write code for the following

1. Declare a variable called x and initialize it with the string "Hello".
2. Declare a variable called y and initialize it with the property length of x.
3. Declare a variable called z and initialize it with the result of calling the method toUpperCase on x
4. Declare a function called myFunction. This function should take two arguments, and should call the second argument with the first argument as its argument. Then, declare a variable called f and initialize it with an empty anonymous function, and call myFunction with the arguments 10 and f.

14. Explain as precisely as possible (in English) what the following code does, line by line

(Tip: it should look like the items in the previous question!)

1
2
3
4
5
let s = "HackYourFuture";
let i = s.indexOf("Your");
function sum(a, b) { return a + b; }
let s = sum(4, 5);
let r = Math.sqrt(s);

15. Indicate for each of these whether it is an expression or a statement:

1. l
2. l = 4;
3. l == 4
4. if (l == 4) { console.log("yes"); } E. console.log("yes"); F. "yes" G. console.log(l == 4 ? "yes" : "no") H. function a() { return 4; } I. let a = function () { return 4; }

16. How can you tell whether something is a statement?

17. How can you tell whether something is an expression

Given the following code:

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
let s = "Hello".toLowerCase();
let l = s.length;

function sum(a, b) {
  return a + b;
}
let max = function (a, b) {
  return a > b ? a : b;
}

let s1 = sum(4, 5);
let s2 = 4 + 5;

if (s2 == s1) {
  console.log("same");
} else {
  console.log("not same");
}

18. List all 11 statements in the code above

19. List all 28 expressions in the code above (BONUS!)