JavaScript Control Statements

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Questions and Answers

What happens if a break statement is omitted after a case statement in a switch structure?

The program will automatically stop executing.

An error will be thrown by the compiler.

The program will skip all subsequent cases.

It will cause the following case to be executed. (correct)

What is true about 'bunching together' case statements in a switch statement?

Bunched cases allow for different outcomes based on conditions.

Each case must have its own separate statements.

Bunched cases can execute the same block of statements. (correct)

Bunching cases requires a default statement to be present.

What does the default case in a switch statement do?

It executes actions if none of the other cases are satisfied. (correct)

It must always be the first case executed.

It is mandatory to include in every switch statement.

It can only execute one statement.

In the context of a switch statement, what will happen if the last case does not have a break statement?

The program control will pass to the next statement after the switch. (C) Signup and view all the answers

Which operator is closely related to the if…else statement and adopts a concise form?

Conditional operator (A) Signup and view all the answers

Which of the following values is considered falsy?

"" (B), null (D) Signup and view all the answers

Which of the following is true about logical values in JavaScript?

Objects are always considered truthy. (D) Signup and view all the answers

How does the parseFloat() function behave when encountering an invalid character?

It stops parsing at the invalid character. (B) Signup and view all the answers

Which operator follows the left to right associativity rule in the context of JavaScript operations?

|| (A), && (B), == (C), ?: (D) Signup and view all the answers

What effect does a fatal logic error have on a JavaScript script?

It results in the script quitting without executing any further. (A) Signup and view all the answers

When a variable is declared but not initialized, what value is it assigned?

undefined (D) Signup and view all the answers

Which of the following describes the behavior of whitespace characters in JavaScript?

They are completely ignored by the interpreter. (A) Signup and view all the answers

What is the main role of the parseInt() function?

To parse a string and return an integer (D) Signup and view all the answers

What will the value of parseFloat(' 3.14abc ') return?

3.14 (B) Signup and view all the answers

What will parseInt('27.95') return?

27 (C) Signup and view all the answers

What is the primary purpose of the if statement in JavaScript?

To execute a single action if a condition is true or skip it if false (D) Signup and view all the answers

Which of the following control statements is considered a double-selection statement?

The if...else statement (B) Signup and view all the answers

What happens if parseInt encounters a non-numeric character in a string?

It returns the integer up to that point (A) Signup and view all the answers

What distinguishes a repetition structure in JavaScript?

It retains control in a block of code while a condition is satisfied (A) Signup and view all the answers

What is indicated by the value NaN in JavaScript?

The value is Not a Number (D) Signup and view all the answers

In which scenarios could you encounter a logic error that produces NaN?

When a variable is not initialized before use (C) Signup and view all the answers

What type of control statement is the switch statement categorized as?

Multiple-selection statement (C) Signup and view all the answers

What happens during the page load event?

Event listeners are activated. (B), The UI elements are rendered on the screen. (D) Signup and view all the answers

What is the purpose of the isNaN() function in JavaScript?

To determine if a value is Not a Number (D) Signup and view all the answers

What are the components required in a try statement for error handling?

A try block and optionally a catch block (B) Signup and view all the answers

What is the role of the increment and decrement operators in JavaScript control statements?

To increase or decrease the value of a variable by one (B) Signup and view all the answers

When implementing JavaScript functionality, which of the following is essential?

Identifying necessary functions for each event listener. (C) Signup and view all the answers

Counter-controlled repetition is primarily based on which of the following?

A predetermined limit set by the programmer (A) Signup and view all the answers

In the context of control statements, what do named blocks allow a programmer to do?

Pass control from a sequence of statements to a named block and back (D) Signup and view all the answers

Which elements typically contribute to JavaScript functionality in an application?

Form controls and displayed messages. (B) Signup and view all the answers

Which statement best describes the while loop in JavaScript?

It executes statements repeatedly as long as a condition is true (B) Signup and view all the answers

What occurs if both catch and finally blocks are used in a try statement?

Both blocks execute in the given order (D) Signup and view all the answers

What approach is recommended for creating event listeners in JavaScript?

Apply the object.createEventListener() syntax. (D) Signup and view all the answers

What is one of the key steps in structuring a JavaScript lab?

Think methodically about implementation and requirements. (C) Signup and view all the answers

Why is it important to follow coding and naming conventions in JavaScript labs?

To ensure readability and maintainability. (A) Signup and view all the answers

What should be avoided when creating event listeners in JavaScript?

Utilizing inline JavaScript syntax. (D) Signup and view all the answers

What should be considered when planning event listeners for an application?

The need for additional, less obvious event listeners. (C) Signup and view all the answers

Study Notes

Control Statements in JavaScript

Transfer of control refers to changing the execution order of statements.
Four fundamental control statements in JavaScript: sequence, selection, repetition, and named blocks.
Sequential execution processes statements in the order they are written.
Selection allows the execution of statements based on conditions using if, if...else, and switch constructs.
Repetition executes statements repeatedly while a specified condition remains true.

Selection Structures

if statement: Executes actions if a condition is true; otherwise, skips it (single-selection).
if...else statement: Conducts different actions based on a true or false condition (double-selection).
switch statement: Selects among multiple options based on the value of an expression (multiple-selection).
Each case in a switch statement should end with a break to avoid logical errors, except for the last case.

Syntax of Switch Statement

General structure is:

switch (expression) {
  case label:
    // statements
    break;
  ...
  default:
    // statements
}

Case labels can be grouped to execute the same set of actions.

Conditional Operator

The conditional operator (?:) replaces simpler if...else statements and takes the form condition ? exprIfTrue : exprIfFalse.

Truthy and Falsy Values

Non-zero numbers, non-empty strings, and all objects are considered truthy.
Zero, empty strings, null, and undefined variables are considered falsy.

JavaScript Coding Practices

Whitespace in scripts is ignored; consistent indentation enhances readability.
Logic errors occur during the execution, affecting the output without causing a script to stop.
Initializing variables is crucial to avoid NaN errors.

Useful Validation Methods

parseFloat(): Converts a string to a floating-point number, ignores invalid characters post-conversion point.
parseInt(): Parses strings to return integers based on a specified radix; ignores invalid characters and truncates floating-point values.
isNaN(): Determines if a value is NaN, returning true or false.

Error Handling in JavaScript

Try...Catch statements manage errors and exceptions effectively.
A try block must be followed by either a catch or finally block; both can exist.

Designing JavaScript Functions

Identify user interaction controls on the web, such as form inputs.
Determine necessary event listeners and their scope within the user interface.
Implement and structure functions based on identified controls and validation needs.

Best Practices in JavaScript Labs

Adhere to coding and naming conventions strictly.
Avoid inline event handlers; prefer using addEventListener for better practice and compliance with standards.
Document all interactions and validate inputs systematically for robust application design.

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Description

This quiz explores Chapters 7 and 8 of 'How to Program, 5/e' focused on JavaScript control statements. Participants will learn essential problem-solving techniques and algorithms, including the use of selection statements and repetition constructs such as while loops. Test your knowledge on how to implement these concepts effectively in programming.

JavaScript Control Statements - Chapters 7 & 8

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