exercises.md

JavaScript fundamentals - exercises

Q1

Given the following code:

var s = "Hello";
var x = s.toLowerCase();
var l = s.length;

What are the types of the following?

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

Q2

In var x = 5 + 6;, what is +?

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

Q3

In var x = 5 + 6;, what is var?

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

Q4

Given the following code:

var x = z[y];

What is y?

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

Q5

Given the following code:

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

What is y?

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

Q6

Given the following code:

var joe = {
  name: "Joe",
  age: 24,
};
var joesName = joe.name;
var joesAge = joe["age"];

• What is 'age' in the last line?
  1. Index
  2. Key
  3. Array
  4. Object
• What are name and age of the object joe?
  1. Index
  2. Key
  3. Object
  4. Property

Q7

Given the following code:

var y = "length";
var x = [1, 2, 3];
var z = x[y];

What is y?

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

Q8

What is the element for index 1 in array x?

Q9

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

Q10

What is the name of these functions?

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

Q11

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

Q12

Write a function call that passes three arguments.

Q13

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.

Q14

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!)

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

Q15

For each of these, indicate whether it is an expression or a statement:

1. l
2. l = 4;
3. l == 4
4. if (l == 4) { console.log("yes"); }
5. console.log("yes");
6. "yes"
7. console.log(l == 4 ? "yes" : "no")
8. function a() { return 4; }
9. var a = function () { return 4; }

Q16

How can you tell whether something is a statement?

Q17

How can you tell whether something is an expression?

Q18

Given the following code:

var s = "Hello".toLowerCase();
var l = s.length;

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

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

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

List all 11 statements in the code above.

Q19

Bonus question!

List all 28 expressions in the code from Q18.