JavaScript Logical Operators: AND and OR

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Questions and Answers

How do you create a new array with 10 boxes without any elements inside?

Declaring an array without assigning any values (correct)

Using array.unshift() 10 times

Declaring an array with 10 undefined elements

Using array.push() 10 times

What is the default separator used in the array.join() method?

Semicolon

Space

Period

Comma (correct)

What is the return value of the array.pop() method?

The removed element (correct)

The size of the array after removal

An empty array

The index of the removed element

What is the purpose of the array.length property?

To get the size of the array Signup and view all the answers

How do you add a new element to the end of an array?

Using array.push() Signup and view all the answers

What is the purpose of the array.concat() method?

To combine two arrays into one Signup and view all the answers

What is the index of the first box in an array?

0 Signup and view all the answers

What is the purpose of short-circuit in AND operation in JavaScript?

To optimize the evaluation process by skipping unnecessary checks Signup and view all the answers

What is the result of an OR operation if both inputs are false?

False Signup and view all the answers

What is an array in JavaScript?

A linear continuous storage of data Signup and view all the answers

What is the purpose of the NOT operator in JavaScript?

To negate the result of a boolean operation Signup and view all the answers

What is the significance of the underscore character in JavaScript identifiers?

It can be used as the first character of a variable name Signup and view all the answers

What is the data type of the variable 'big_number' in the following code: var big_number = 123e5;

Number Signup and view all the answers

What is the difference between the variables 'myBool' and 'myString' in the following code?

myBool is a Boolean and myString is a String Signup and view all the answers

What is the purpose of the curly braces in the following code: var person = { firstName:"John", lastName:"Doe", age:50, eyeColor:"blue" };

To define an object Signup and view all the answers

What happens to the variable 'carName' in the following code: var carName = "Volvo"; var carName;

The variable 'carName' retains its original value Signup and view all the answers

What is the significance of JavaScript being dynamically typed?

It means that variables can change data type during execution Signup and view all the answers

Study Notes

Logical Operators

&& operator: returns true if both inputs are true, otherwise false
Short-Circuit in &&: JavaScript stops checking if the first input is false
|| operator: returns false if both inputs are false, otherwise true
Short-Circuit in ||: JavaScript stops checking if the first input is true
! operator: returns the opposite of the input

Arrays

An array is a linear, continuous storage of data
Each element in an array has a unique index, starting from 0
Arrays can be thought of as a group of boxes
How to create an array: var myArray = [element1, element2, element3];

JavaScript Identifiers

All JavaScript variables must have unique names (identifiers)
Identifiers can be short names (like x, y) or more descriptive names (age, sum, totalVolume)
Rules for constructing names:
- Can contain letters, digits, underscores, and dollar signs
- Must begin with a letter, $, or _
- Case-sensitive (y and Y are different variables)
- Cannot use reserved words (like JavaScript keywords)

JavaScript Data Types

Number: can be written with or without decimals, and can use scientific notation
String: a sequence of characters, can use single or double quotes
Boolean: can only be true or false
Object: can be written with curly braces, and have properties as name:value pairs
Function: a block of code that can be executed
Null and undefined: cannot contain values

Working with Arrays

array.join(separator): converts an array into a string, with a separator (default is ",")
Retrieving an element from an array: array[index]
Changing an element in an array: array[index] = new_value
array.length: returns the size of an array (number of elements)
array.push(element): adds a new element to the end of an array
array.unshift(element): adds a new element to the front of an array
array.pop(): removes an element from the end of an array and returns it
array.shift(): removes an element from the front of an array and returns it
array1.concat(array2): combines two arrays into one

Generating Random Numbers

Math.random(): generates a random number between 0 and 1
Setting up the range: multiply the result by a number to get the desired range

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Description

Test your understanding of JavaScript's logical operators AND (&&) and OR (||), including their short-circuit behavior. Learn how JavaScript evaluates these operators and how they can be used effectively in your code.