Sample Coding Questions

Question 1

When logical OR, if one of the sides is TRUE it will return…

Answer 1

True!
Example:

true || false 
// it will evaluate to true!

Question 2

When logical AND, if one of the sides is false it will return…

Answer 2

False!
Example:

true && false
// will evaluate to false

Question 3

Syntax of the IF statement

Answer 3

if (condition) {
  //  block of code to be executed if the condition is true
}

Question 4

Make a Good Day greeting if the hour is less then 18:00

Answer 4

if (hour < 18) {
greeting = “Good day”;
}

Question 5

If…else syntax

Answer 5

if (condition) {
  //  block of code to be executed if the condition is true
} else {
  //  block of code to be executed if the condition is false
}

Question 6

Else if syntax

Answer 6

if (condition1) {
  //  block of code to be executed if condition1 is true
} else if (condition2) {
  //  block of code to be executed if the condition1 is false and condition2 is true
} else {
  //  block of code to be executed if the condition1 is false and condition2 is false
}

Question 7

Why use the Switch Statement?

Answer 7

Use the switch statement to select one of many code blocks to be executed.

Question 8

Switch statement syntax

Answer 8

switch(expression) {
  case x:
    // code block
    break;
  case y:
    // code block
    break;
  default:
    // code block
}

Always have a DEFAULT!

Question 9

How does the switch statement work?

Answer 9

The switch expression is evaluated once.
The value of the expression is compared with the values of each case.
If there is a match, the associated block of code is executed.
If there is no match, the default code block is executed.

Question 10

Example of Switch statement

Answer 10

The getDay() method returns the weekday as a number between 0 and 6.

(Sunday=0, Monday=1, Tuesday=2 ..)

switch (new Date().getDay()) {
  case 0:
    day = "Sunday";
    break;
  case 1:
    day = "Monday";
    break;
  case 2:
     day = "Tuesday";
    break;
  case 3:
    day = "Wednesday";
    break;
  case 4:
    day = "Thursday";
    break;
  case 5:
    day = "Friday";
    break;
  case 6:
    day = "Saturday";
}

Question 11

What is the break keyword meant for in a switch statement?

Answer 11

When JavaScript reaches a break keyword, it breaks out of the switch block.

This will stop the execution inside the switch block.

It is not necessary to break the last case in a switch block. The block breaks (ends) there anyway.

Question 12

Possible Exam Question….

Does the default case has to be the last case in a switch block?

Answer 12

No
IF default is not the last case in the switch block, remember to END the default case with a break.

Example: 
switch (new Date().getDay()) {
  default:
    text = "Looking forward to the Weekend";
    break;
  case 6:
    text = "Today is Saturday";
    break;
  case 0:
    text = "Today is Sunday";
}

Question 13

What happends if multiple cases matches a case value (Switch statement)

Answer 13

If multiple cases matches a case value, the first case is selected.

If no matching cases are found, the program continues to the default label.

If no default label is found, the program continues to the statement(s) after the switch.

Question 14

Switch cases use strict comparison (===).

Answer 14

The values must be of the same type to match.

A strict comparison can only be true if the operands are of the same type.

Question 15

What will happen if the break statements in the following code block are replaced with the continue statements? (Assume that the value of test is ‘C’.)

switch(test) {
case ‘A’: alert(“Excellent.”); break;
case ‘B’: alert(“Good.”); break;
case ‘C’: alert(“Average.”); break;
case ‘D’: alert(“Below average.”); break;
default: (“Disqualified.”); break;
}

Answer 15

The given code block will display the SyntaxError: Illegal continue statement: no surrounding iteration statement message in the console window, because of the continue statement, which can be used in loops (or iteration statements).

Question 16

Consider X and Z to be true and Y to be false, which of the following conditions will return false?

Y || Z
Y && Z
X && Z
X || Y

Answer 16

The condition Y && Z will return false, because the AND operator returns true only if both the operands are true. And, in this case, the operand Y is false

Question 17

Which of the following statements will execute only if the conditions A and B are true?
 	A.	if (A) && if (B)
 	B.	if (A || B)
 	C.	if (A) & if (B)
        D.	if (A && B)

Answer 17

The && logical operator is used to combine expressions so that the entire expression returns true only if all the individual conditions in the expression are true.

Question 18

What is is true of control structures?

Answer 18

They make decisions based on Boolean values.

Question 19

What can be a substitute for the nested if-else statements?

Answer 19

The switch statements can be used to substitute a nested if-else block. The conditions that are being tested in the if-else block can be specified as a case in the switch block

Question 20

What is the purpose of the switch statement?

Answer 20

To compare a value against other values, to search for a match.

The switch statement compares a value against other values, to search for a match. If a match is found, then the code associated with the match will execute. The break statement is then used to exit the switch block of code. Essentially, the switch statement functions the same as multiple if-else clauses within an if statement. However, the switch statement is more readable and allows you to specify a default set of statements to execute if no match is foun

Question 21

What is true about the do-while statement?

Answer 21

The do-while statement operates like the while statement, with one key difference. The do-while statement does not check the conditional expression until after the first time through the loop, guaranteeing that the code within the curly braces will execute at least once. A do-while loop can accomplish some tasks that the while loop cannot. The difference between the two control structures is that the do-while loop will execute its code at least one time, regardless of the Boolean value returned by the test condition.

Question 22

Consider the following code:

for (X; Y; Z)

What does Y represent in this statement?

Answer 22

In the given statement for (X; Y; Z), Y is the condition under which the loop will execute. X is the loop counter variable initialization expression. Z is the expression that increments or decrements the loop counter

Question 23

Consider the following code snippet:

var x = 100;
  while (x > 5) {
    x--;
  }

What will be the value of x after the execution of the given code snippet?

Answer 23

The value of x after the execution of this code will be 5. The condition under which the while statement executes is x > 5, so the last condition of the while loop will be executed when x has a value of 6. Now, the code inside the while statement will execute for x = 6, which is greater than 5, and the value of x will be decremented by 1 one more time making its value 5

Question 24

Consider the following code:

var myPet= "rabbit";
switch (myPet) {
   case "Rabbit":
   document.write("My pet is a Rabbit.");
   break;
   case "Frog":
   document.write("My pet is a Frog.");
   break;
   default:
   document.write("I do not have a pet.");
}

Answer 24

JavaScript is a case-sensitive language. Thus, the default output (I do not have a pet.) will be the result because the variable rabbit did not match with the variable Rabbit due to the case of the letter ‘R’

Question 25

What is a way to exit a loop that would otherwise continue to execute?

Answer 25

A way to exit a loop that would otherwise continue to execute is to use the break statement. Usually, you will find the break keyword inside an if clause. If a certain condition is reached, the program will break out of the loop. If not, the loop will continue. You can use the break statement within the for, while, and do...while loops, as well as with the switch statement

Question 26

Which JavaScript statement is used to force the flow of control back to the top of a loop?

Answer 26

continue Feedback: The continue statement is used to force the flow of control back to the top of a loop. The continue statement can be considered as a "skip" or bypass command. When execution hits the continue statement, all statements between it and the end of the loop block are skipped, and execution returns to the top of the loop. The test condition for the loop is then evaluated to determine whether the loop should execute again. The continue statement can be used only within the for or the while loop

Question 27

Consider the following code: var j = 0, i; for (i = 0; i < 10; i++) { document.write(i + " + "); j += i; } document.write("=" + j); What is the output when this script is run in the browser?

Answer 27

The loop executes 10 times and sums the numbers using j. An extra addition operator (+) appears because the document.write() method includes it after every number. It performs addition rather than concatenation because it recognizes the numbers are not string

Question 28

Is the number of iterations in a do-while loop always one more than the while loop?

Answer 28

Not always. Here both iterate 1 time: ``` // while loop var x = 1; while (x > 0) { document.write("a"); x--; } // dowhile loop var x = 1; do { document.write("a"); x--; ```

Question 29

Which JavaScript statement should you use to test for a single condition and branch to a process?

Answer 29

The if and if...else statements provide the ability to branch to one of two or more processes, depending on the result of some test condition that you have scripted. The if statement is used to test for a single condition.

Question 30

Consider the following code block: if (test == 10) { alert("Disqualified."); } else if (test == 25) { alert("Passed with grace marks."); } else if (test == 40) { alert("Passed."); } else if (test == 50) { alert("Passed with honors."); } else { alert("Inconclusive score."); }

Answer 30

The switch statement is best suited to replace the given code of segment. while and for are looping statements, therefore they will not be of much help. The problem with if statements without the else block is the last alert "inconclusive score." If all other conditions fail, the else block must execute. Realizing this logic through if statements only will be inefficien

Question 31

Consider the following code snippet: if (example = 25) { document.write("Correct answer."); } else { document.write("Wrong answer."); } Assuming the value of example is 10, what will be the output of the code snippet?

Answer 31

In the if block, the test expression example = 25 will always return 25, because instead of the equality comparison operator (==), the assignment operator (=) is used.

Question 32

Will this run? Look at the missing curly braces.... if (timerMinutes == 10) alert("Time Expired!");

Answer 32

Yes, it will! If the code associated with a test condition consists of just one line, you can omit the curly braces. There should be no quotation marks around the variable named (timerMinutes)

Question 33

How does JS evaluate the day's placement in a week?

Answer 33

It doesn't. It compares the values of the strings letter-by-letter and returns the value in the Boolean form. Example: ``` var day = "Thursday"; if(day < "Wednesday"){ window.alert("It's before today"); } else{ window.alert("It's after today") } ``` In this case, the string Thursday has the first letter as 'T' which is less than the letter 'W' of the string Wednesday, so the value Thursday is less than Wednesday. So, the operation evaluates to true and the script displays the output as It's before today

Question 34

Consider the following code: ``` var test = 100; if(test <= 6 && test >= 200 || test != 2) { window.alert("Good"); } else{ window.alert("Bad"); } ```

Answer 34

The code is well-formed, so the window alert box will appear and display Good. Because this script uses an if/else statement, only one alert box will appear. The value of test (100) is not equal to 2 (see the last condition after the || operator), so the entire expression evaluates to true. Thus, the Boolean evaluates to true so the value Good is displayed.

Question 35

What will be the output of the following code block? for (a = 10; a > 0; a--) { document.write(a + ", "); if (a == 5) break; }

Answer 35

The for block will execute as usual, displaying the value of a at each iteration. But at the sixth iteration, the condition inside the if statement will result true, and the break; statement will execute, causing the loop to end. (

Question 36

Different Kinds of Loops | JavaScript supports different kinds of loops:

Answer 36

for - loops through a block of code a number of times for/in - loops through the properties of an object for/of - loops through the values of an iterable object while - loops through a block of code while a specified condition is true do/while - also loops through a block of code while a specified condition is true

Question 37

What does the forEach method?

Answer 37

``` The forEach() method calls a function for each element in an array. The forEach() method is not executed for empty elements. ```

Question 38

Example of forEach method

Answer 38

``` let sum = 0; const numbers = [65, 44, 12, 4]; numbers.forEach(myFunction); ``` document.getElementById("demo").innerHTML = sum; ``` function myFunction(item) { sum += item; } ```

Question 39

Using an array literal is the easiest way to create a JavaScript Array.

Answer 39

``` const cars = [ "Saab", "Volvo", "BMW" ]; ```

Question 40

It is considered good practice to name constructor functions with an upper-case first letter.

Answer 40

True

Question 41

Example of the constructor (with the keyword new)

Answer 41

``` // Constructor function for Person objects function Person(first, last, age, eye) { this.firstName = first; this.lastName = last; this.age = age; this.eyeColor = eye; } ``` ``` // Create a Person object const myFather = new Person("John", "Doe", 50, "blue"); ```

Question 42

Add property to an Object

Answer 42

myFather.nationality = "English";

Question 43

Add Method to an Object

Answer 43

myFather.name = function () { return this.firstName + " " + this.lastName; };

Question 44

Can you add a property to a constructor?

Answer 44

No. To add a new property to a constructor, you must add it to the constructor function: ``` function Person(first, last, age, eyecolor) { this.firstName = first; this.lastName = last; this.age = age; this.eyeColor = eyecolor; this.nationality = "English"; } ```

Question 45

Consider the following code block: ``` function sample(a, b) { a++; b++; return a + b; } ``` Which of the following expressions is an equivalent of the sample() function?

Answer 45

The following expression represents an arrow function: var sample = (m, n) => ++m + ++n; Other expressions are either syntactically incorrect or will return incorrect values of variables. In the given code block, the value of the variables a and b is incremented before returning. The pre-increment operators modify the value of the variables before using them. The following expression will not increment the value before returning: var sample = function (m, n) { return m++ + n++; }

Question 46

What is an argument in JavaScript?

Answer 46

A value passed into a function from outside the function. Also called parameters

Question 47

When does Event capturing start?

Answer 47

Event capturing starts at the highest level in the DOM hierarchy tree (generally, the Window object

Question 48

Consider the following code: ``` function dateTodayTomorrow(a, b){ a.concat(b); return a.valueOf(); } alert(dateTodayTomorrow('Wednesday','Thursday')); ``` What will the alert box display when this script is run in a browser?

Answer 48

The alert box will display the value of a only i.e. Wednesday, even though in the previous line there was a concatenation. But the concatenated value is not assigned to the variable a, so the initial value of the variable a will not be changed. Thus, Wednesday will be displayed in the alert box when the given script is run in the browser

Question 49

Are functions hoisted?

Answer 49

Yes. When a page is rendered, the function definitions are hoisted and all functions are created at runtime.

Question 50

The parseInt() Method

Answer 50

parseInt() parses a string and returns a whole number (integer)

Question 51

The parseFloat() Method

Answer 51

parseFloat() parses a string and returns a number. parseFloat("10") ---> 10

Question 52

Which JavaScript property is used to add new properties and methods to objects?

Answer 52

The prototype property is used to add new properties and methods to objects. New methods and functions are attached to the prototype property of the object. These methods and functions are then automatically added to the object itself.

Question 53

All JavaScript objects inherit properties and methods from a prototype:

Answer 53

Date objects inherit from Date.prototype Array objects inherit from Array.prototype Person objects inherit from Person.prototype The Object.prototype is on the top of the prototype inheritance chain:

Question 54

Prototype property Example ( add a property)

Answer 54

``` function Person(first, last, age, eyecolor) { this.firstName = first; this.lastName = last; this.age = age; this.eyeColor = eyecolor; } ``` Person.prototype.nationality = "English";

Question 55

Attention:

Answer 55

Only modify your own prototypes. Never modify the prototypes of standard JavaScript objects.

Question 56

How does a global variable differ from a local variable?

Answer 56

You can access a global variable value from any function or block that you define on the HTML page.

Question 57

To instantiate and then populate the properties of each new instance with actual data, you must _________ _________.

Answer 57

declare variables

Question 58

Target a frame, you need to know..

Answer 58

the frame's number in the frames array OR the frame's name

Question 59

Which of the following is the correct way to test for the presence of a cookie?

Answer 59

alert(document.cookie);

Question 60

Frames are arranged in a parent child hierarchy. With this in mind, in JavaScript, which keyword targets the parent of all parents in a frameset?

Answer 60

top

Question 61

A (an) __________ is a value or expression containing data or code that is passed on to a function or procedure.

Answer 61

argument

Question 62

You must declare variables that will become object references to a newly instantiated objects to _____________________

Answer 62

instantiate and then populate the properties of each new instance with actual data

Question 63

Jennie wants to retrieve the MIME information about her Web form. Which property of the form object retrieves this information?

Answer 63

encoding

Question 64

In JavaScript, what is the purpose of the form object?

Answer 64

The form object represents an HTML form in JavaScript. This object is used to access all properties of the form, most importantly, the elements that compose the form.

Question 65

How can you check if a user's browser has Java enabled or not?

Answer 65

The javaEnabled() method of the navigator object can be used to check if a user's browser has Java enabled or not. This method returns a Boolean value in return (true or false)

Question 66

Which line of code will allow you to redirect the browser to the page which you were previously viewing?

Answer 66

history.back();

Question 67

What is the limitation of a Virtual DOM?

Answer 67

Changes made to the Virtual DOM are not directly reflected on the webpage.

Question 68

What is the one property associated with the history object?

Answer 68

length

Question 69

Which object can be used to access cookies?

Answer 69

The documetn object has the cookie property

Question 70

What is the purpose of the location object?

Answer 70

To specify URLs in the script.

Question 71

Which code is the JavaScript equivalent of clicking a browser's back button?

Answer 71

history.go(-1);

Question 72

What will protocol display?

Answer 72

The alert will display http:. The properties of the location object relate to the various pieces of information that form a complete URL. In many applications, accessing this information is extremely important. These properties allow the developer easy access to this data without having to perform rather complex string manipulation. The elements of the URL are identified as follows: protocol://hostname:port/pathname/search#hash where, protocol represents http, hostname:port represents www.myweb.com, pathname represents faq/answers, and search#hash represents protocol=email in the given URL

Question 73

What is the container of the form object?

Answer 73

document

Question 74

Which JavaScript object represents the frame of the browser and the mechanisms associated with it?

Answer 74

window

Question 75

How to bring a window object to the top?

Answer 75

A new browser window can be brought to the forefront by using the window.focus() method,

Question 76

Which method of the history object is used to create a new history entry?

Answer 76

The pushState() method of the history object is used to create new history entries

Question 77

What is diffing?

Answer 77

The process of comparing the new Virtual DOM with its previous version for identifying the elements (or objects) of the Virtual DOM that have changed (or updated) is called diffing. In React, after diffing, only those objects in the real DOM that have changed are updated

Question 78

How to check if image has loaded?

Answer 78

The complete property of the image object can be used to check if the referenced image has been loaded completely in the browser window.

Question 79

How many arguments does the generic syntax for the window.open() method use?

Answer 79

The generic syntax for the window.open() method uses three arguments, namely, a URL, a window name, and a list of window features

Question 80

Reg Exp

Answer 80

A regular expression is a sequence of characters that forms a search pattern. The search pattern can be used for text search and text replace operations.

Question 81

Why use i in a string search (Reg Exp)

Answer 81

To do a case insensitve search

Question 82

Reg Exp modifiers

Answer 82

i Perform case-insensitive matching g Perform a global match (find all matches rather than stopping after the first match) m Perform multiline matching

Question 83

test() in Reg Ex

Answer 83

The test() method is a RegExp expression method. It searches a string for a pattern, and returns true or false, depending on the result.

Question 84

You need to create a comma-delimited list from an array of values. Which function will accomplish this?

Answer 84

The correct function is myArray.join(",");. The join() method creates a string of an array's values. The join() method requires a single argument: The character that will act as the separator for the element's values.

Question 85

Consider the following code: var firstArray = ["Sabrina", "Kelly", "Jill"] var secondArray = firstArray; secondArray.push("Kris"); alert(secondArray); What output will be displayed in the alert box when this script is run in the browser?

Answer 85

The alert box will display Sabrina, Kelly, Jill, Kris. The push method adds the element to the end of the array.

Question 86

How do the shift() and pop() methods differ?

Answer 86

The shift() method works at the first element in the array. It removes and returns the first element in the array and then shifts the contents (index) of the array accordingly. The pop() method works on the last element in the array. It removes the last element from the array and returns it to the calling statement

Question 87

How can you extract the username portion of the email address given in the following line of code?

Answer 87

The correct code is email.substring(0, email.indexOf("@"));. The substring() method will grab the characters starting with the first one (in index position 0) up to the character before the @ sign, which is located using the indexOf() property. The substring() method extracts the string up to the index position of the second parameter i.e. @, not including that character.

Question 88

Which code snippet can be used to display the current date?

Answer 88

You can use date and time information in JavaScript through the Date object. To use any date or time information, you must create a new instance or copy of the Date object using the new keyword. Considering this, the following code snippet is used to display the current date: ``` var myDate = new Date(); alert(myDate); ```

Question 89

Consider the following code: var nurseryRhyme = "Mary had a little lamb"; How would you find the position of the last letter "a" in the given code?

Answer 89

The correct code and syntax is: nurseryRhyme.lastIndexOf("a"); The lastIndexOf method will return the last letter "a" in the string.

Question 90

When you need to run a function after a certain amount of time, which method would you use?

Answer 90

The correct statement is setTimeout(function, time);. To have a method or command repeat after a set amount of time, you use the setTimeout() method. It passes the parameters for the function to run and the time to wait before running it

Question 91

What does the map() return?

Answer 91

The map() method returns an array with the results of a function called for each element in an array. (

Question 92

An interface that you are developing will display an array in a list format. You want to allow the user to flip the list, making the first item last and the last item first, and reversing the order of all items. Which line of code will help you to achieve the task?

Answer 92

The correct statement is arrayList.reverse();. Arrays have a method that can be applied to them to flip or reverse the order. The reverse() method does not take any parameters. It will change the array so that the first entry is now last, the second entry is second to last, the last entry is first, and so forth

Question 93

What will be the output of the following expression: "Hi there!".split("e")?

Answer 93

The split() method splits a string using the specified character or regular expression and returns an array of substrings. Here's the syntax of the split() method: string.split(split_character, number_of_splits); where, split_character specifies the character over which the string is split and number_of_splits specifies the number of items (after the split) to be included in the returned array. In the given expression, the split_character is e, so the expression will get split where the character e occurs. Since, the given expression contains two e's, therefore, the number_of_splits that takes place will be twice. So, the output will be ["Hi th", "r", "!"].

Question 94

What is the purpose of the prototype property of the String objects?

Answer 94

It is used to create your own methods and properties of the String object.

Question 95

In JavaScript, the String, Math, Array, Date, and RegExp objects are called

Answer 95

In JavaScript, the String, Math, Array, Date, and RegExp objects are called language objects.

Question 96

Consider the following code: ``` var firstArray = ["Sabrina", "Kelly", "Jill"]; var secondArray = firstArray; secondArray = secondArray.join("Kris"); alert(secondArray); ``` What will the alert box display when this script is run in the browser?

Answer 96

The alert box will display SabrinaKrisKellyKrisJill. The join method will add all of the elements in the array into a string using a parameter as the separator. Because Kris was the parameter, Kris was used instead of a comma, which is the default.

Question 97

Consider the following code: var nurseryRhyme = "Mary had a little lamb"; How would you find the letter at the seventh position of the given string?

Answer 97

You can find the letter at the seventh position of the given string using the charAt() method. The charAt() method will find the character at the specified position. For the given code, the correct syntax is nurseryRhyme.charAt(6);. You can count position beginning with 0, not 1.