Week-4

Question 1

Javascript is always executed sequentially

Answer 1

True

Question 2

HTML:

Is this HTML valid?

Answer 2

No, it’s missing a closing ‘script’ tag. It must always be there.

Question 3

Identify valid Javascript code snippet(s)

Answer 3

a) var x = "Hello world!";
Regular variable declaration.
b) var x = function () {
  console.log("Hello World");
  return;
};
It's valid. The 'return' statement here doesn't do much as the function will return anyway without it.
c) var x = function () {
  console.log("Hello World");
  return;
};
x();
Valid. The last line simply executes/invokes the function.
d) var x = function () {
  console.log("Hello World");
  return;
};
x = "hello, I am a new value!";
Valid. Javascript has dynamic typing, so 'x' can be a function and then can change to be a regular string.

Question 4

An object in Javascript is simply a collection of name/value pairs.

Answer 4

True

Question 5

In Javascript, a primitive type can store only 1 name/value pair at a time.

Answer 5

False as Primitive values are NOT name/value pairs. They are single values.

Question 6

Strict equality operator (===) differs from regular equality operator (==) in that it checks if both values on its right and left are of the same type first. If they are not, it doesn’t try to coerce them to be the same value and just returns false.

Answer 6

True

Question 7

JS:
var x = 10;
if ( (null) || (console.log(“Hello”)) || x > 5 ) {
console.log(“Hello”);
}
How many times will the word ‘Hello’ be printed to the console?

Answer 7

2
Since we are using an OR operator, the ‘if’ statement will stop evaluating conditions after it encounters the very first clause that evaluates to true.
null is false, so we continue
console.log(“Hello”), prints “Hello” to the console and returns nothing, so it’s ‘undefined’ and ‘undefined’ is false, so we continue
x > 5 is true, so we execute the body of the ‘if’ statement and print another “Hello”.
So, the answer is that “Hello” will be printed to the console 2 times.

Question 8

Defining a variable as an Object Literal accomplishes pretty much the same thing as defining a variable equal to ‘new Object()’. However, it’s faster and easier to type up an object literal.

Answer 8

True

Question 9

What is the output for the following Javascript code:
function makeMultiplier(multiplier) {
  var myFunFunc = function (x) {
    return multiplier * x;
  };

return myFunFunc;
}

var operation = makeMultiplier(10);
console.log(operation(10));

Answer 9

100

Question 10

Javascript doesn’t allow anything to be passed by reference

Answer 10

False

Objects are passed by reference.

Question 11

Output of:
var x = 5;
var y = x;
x = 10;
console.log(y);

Answer 11

5

as Primitives are copied by value, so ‘y’ is not connected to ‘x’ in any way.

Question 12

Output of JS:
function Dog(name) {
  this.name = name;
}

Dog.prototype.bark = function () {
console.log(this.name + “ likes barking! Bark!”);
}

var max = new Dog("Max", "Buddy");
max.bark();

Answer 12

Max likes barking! Bark!

as The second argument is not used in the function but it’s perfectly legal to pass it in.

Question 13

Output of JS:
var counter = 0;
var myArray = [“Yaakov”, 2, {handle: “yaakovchaikin”}];
for (var i = 0; i < myArray.length; i++) {
counter++;
}
console.log(counter);

Answer 13

3

Question 14

Immediately Invoked Function Expressions are usually used to place code into its own execution context not to conflict with the global scope.

Answer 14

True

Question 15

Code:
1  (function(window) {
2 
3  var obj = {};
4
5  obj.dreamOn = function () {
6   console.log("I want to see the global scope! Let me out!");
7  };
8
9  window.doer = obj;
10 
11 });
12
13 doer.dreamOn();
What (if anything) is missing from this code in order to get it to output the message of the "dreamOn" method?

Answer 15

The attempted IIFE is not being invoked and passed in the window object. It’s missing ‘(window)’ Line 11 right before the semicolon.