Advanced Web Programming - Chapter 9
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Questions and Answers

What is the primary purpose of using arrays in programming as described?

  • To handle lists of data efficiently. (correct)
  • To perform mathematical operations directly.
  • To improve the performance of string manipulations.
  • To create a variable without any assigned values.

How is an array initialized in JavaScript according to the provided example?

  • An array is initialized using open and close brackets with no values. (correct)
  • The array needs a lengthy declaration without brackets.
  • An array is initialized using curly braces with values inside.
  • Array can be initialized using the Array constructor only.

What is the index value of 'Salami' in the given groceries array?

  • 3 (correct)
  • 2
  • 0
  • 4

What would happen if an index value exceeds the length of an array?

<p>It would return undefined. (B)</p> Signup and view all the answers

Which of the following is a correct method to access 'Juice' from the groceries array?

<p>groceries[4] (C)</p> Signup and view all the answers

What does the length property of an array represent?

<p>The count of index values available in the array (D)</p> Signup and view all the answers

What happens when an item is added to the beginning of the array using the unshift method?

<p>The index values of all existing items shift to the right (B)</p> Signup and view all the answers

What is the effect of calling the pop method on an array?

<p>It removes the last item of the array and returns it (D)</p> Signup and view all the answers

Which of the following correctly describes the process of looping through an array from start to finish?

<p>The loop should use the last index to determine the end (A)</p> Signup and view all the answers

If an array named groceries has an initial length of 5, what will its length be after executing groceries.push('Cookies')?

<p>6 (C)</p> Signup and view all the answers

What value is returned by the shift method when called on an array?

<p>The first item of the array (C)</p> Signup and view all the answers

What does the pop method return when called on an array?

<p>The last item of the array (A)</p> Signup and view all the answers

How does the slice method affect the original array?

<p>It creates a new array without modifying the original (C)</p> Signup and view all the answers

What result do both indexOf and lastIndexOf methods return when searching for an item that does not exist in the array?

<p>-1 (A)</p> Signup and view all the answers

What is the primary difference between indexOf and lastIndexOf?

<p>indexOf returns the first occurrence, while lastIndexOf returns the last (A)</p> Signup and view all the answers

What happens to the index positions of items in an array after using the shift method?

<p>They are decremented by 1 (D)</p> Signup and view all the answers

What is the resulting length of an array after calling the unshift method with one item?

<p>One more than before (C)</p> Signup and view all the answers

When using the slice method with parameters (1, 4), which items are included in the new array?

<p>Items at indexes 1, 2, 3 (D)</p> Signup and view all the answers

What will be the value of goodAndBad after executing var goodAndBad = good.concat(bad);?

<p>['Mario', 'Luigi', 'Kirby', 'Yoshi', 'Bowser', 'Goomba', 'Koopa Troopa'] (C)</p> Signup and view all the answers

What will the value of temperature be after executing var temperature = −42;?

<p>-42 (D)</p> Signup and view all the answers

Which of the following correctly uses the modulus operator?

<p>var result = 10 % 3; (D)</p> Signup and view all the answers

How would i be modified after executing i = i - 2; if i was originally 100?

<p>98 (A)</p> Signup and view all the answers

What is the correct order of operations used by JavaScript when evaluating mathematical expressions?

<p>Parenthesis, Exponents, Multiply, Divide, Add, Subtract (A)</p> Signup and view all the answers

Which expression correctly illustrates incrementing a variable i by 1?

<p>i = i + 1; (B), i++; (C)</p> Signup and view all the answers

Flashcards

Array

An ordered list of values (elements).

Array Element

A single value within an array.

Array Index

A number that identifies the position of an element in an array.

Array Literal Notation

Using square brackets to create an array.

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Accessing Array Values

Retrieving an array element using its index.

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Array Length

The total number of elements in an array.

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Empty Array

An array with no elements.

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Array Initialization

Creating an array and giving it an initial set of elements (or none).

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Array.shift()

Removes and returns the first item in an array. All subsequent elements' indexes are decremented.

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Array.push()

Adds an item to the end of an array and returns the new length.

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Array.unshift()

Adds an item to the beginning of an array and returns the new length.

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Array.pop()

Removes and returns the last item in an array.

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Array.slice()

Creates a new array by copying a portion of an existing array.

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Array.indexOf()

Returns the index of the first occurrence of a specified element. Returns -1 if element not found

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Array.lastIndexOf()

Returns the index of the last occurrence of a specified element. Returns -1 if element not found

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Array Concatenation

Combining two arrays into a single array using the concat() method, creating a new array.

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Array Length

The count of items in an array (its size).

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Array index

A number that locates an item in an array.

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concat() method

A JavaScript method used to join two or more arrays and creating a new array containing all elements. It does not modify the original arrays.

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Numbers in JavaScript

Representing numerical values (integers, decimals, and large numbers).

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Accessing array values

Retrieving data from a specific position in an array using its index.

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Looping through arrays

Iterating over the items in an array using a loop like 'for'.

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JavaScript Operators

Symbols (+, -, *, /, %) used to perform mathematical calculations (addition, subtraction, multiplication, division, remainder).

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Adding items (push)

Adding a new item to the end of an array using 'push'.

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Order of Operations

Rules for evaluating expressions involving multiple operators (parentheses, exponents, multiplication/division, addition/subtraction) in a specific sequence.

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Incrementing a Variable

Increasing the value of a variable by a specific amount.

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Adding items (unshift)

Adds a new item to the beginning of an array, and adjusts other indexes.

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Removing items (pop)

Removing the last item from an array and returns it.

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Decrementing a Variable

Decreasing the value of a variable by a specific amount.

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Cumulative Modification

Modifying a variable's value repeatedly using operators. This changes the original variable each time.

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Removing items (shift)

Removing the first item from an array and returns it.

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Array push return value

The push method returns the new length after adding an element.

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Undefined error

A JavaScript error message when accessing an array index outside of its valid range.

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Study Notes

Advanced Web Programming - Chapter 9: Arrays, Numbers

  • Arrays: Used to handle lists of data.
  • Array Properties: Used for common data list tasks.
  • Numbers: Covers different numerical types (e.g., integers, decimals, complex, hexadecimal).
  • Math Object: Provides mathematical functions and constants.

Arrays

  • Real-World Example: A grocery list is a real-world example of an array.
  • Array Values (or Elements): The items in the list that need to be purchased.
  • Array Literal Notation: Using brackets [] to create an array.

Creating Arrays

  • Empty Arrays: Initialize an array with empty brackets []. Eg: var groceries = [];
  • Non-Empty Arrays: Create an array with values inside the brackets, separated by commas. Eg: var groceries = ["milk", "eggs", "frosted flakes"];

Accessing Array Values

  • Index Values: Each item in an array has a numerical index value, starting from 0. Eg: groceries[0] (milk), groceries[1](eggs).
  • Index Value Specification: Access an element by using its index value inside square brackets. Example: groceries[1]

Accessing Multiple Values

  • Iteration using for loop: The for loop can access all items in the array systematically.
  • Length Property: Use the length property of an array to determine its length and iterate across each element of the array up to element prior to the length of the array Example groceries.length

Adding Items to Arrays

  • Push Method: Adds new items to the end of an array. Eg: groceries.push("bananas");
  • Unshift Method: Adds new items to the beginning of an array. Eg: groceries.unshift("yogurt");

Removing Items from Arrays

  • Pop Method: Removes and returns the last item in an array. Eg: lastItem = groceries.pop();
  • Shift Method: Removes and returns the first item in an array. Eg: firstItem = groceries.shift();

Merging Arrays

  • Concat Method: Combines two arrays into a new array, preserving the order. Eg. var goodAndBad = good.concat(bad);

Numbers (JavaScript)

  • Variables using Numbers: Declare variables containing numbers. Examples: var stooges = 3; // integer var pi = 3.14159; // decimal var color= 0x000; // hex var massOfEarth = 5.9742e+24; // scientific notation

Numbers - Operators

  • Mathematical Operators: The +, -, *, / for fundamental operations on numbers. % for remainder (modulus).
  • Parentheses for Order of Operations: Operations within parentheses are performed first.

Incrementing and Decrementing

  • Incrementing: Increasing a number's value.
  • Decrementing: Decreasing a number's value.
  • Increment/Decrement Operators: ++i or i++ – increment operator and --i or i-- – decrement operator. Use the operator at the start or end of the variable to adjust the order in which the calculation is performed.

Special Values

  • NaN: "Not a Number." Result of invalid numerical operation
  • Infinity/Infinity: Represent very large or small numbers respectfully. Return when you divide a number by zero.

The Math Object

  • Functions: Provides various mathematical functions (e.g., sin, cos, tan, sqrt, pow).
  • Constants: Includes common mathematical constants (e.g., Math.PI, Math.E).

Rounding Numbers

  • Rounding Functions: Math.round(), Math.ceil(), Math.floor().

Trigonometric Functions

  • Radians: Trigonometric functions, sin, cos, tan use radians as the input measurement.
  • Convert Degrees to Radians: Convert to the appropriate unit before calculating trigonometric values.

Powers and Square Roots

  • Math.pow(): Raise a number to a power. Eg. Math.pow(2, 4); (2 to the power of 4)
  • Math.exp(): Raise Euler's constant (e) to a power.
  • Math.sqrt(): Calculate the square root of a number.

Absolute Value

  • Math.abs(): Return absolute value of a number.

Random Numbers

  • Math.random(): Returns pseudo random values between 0 and 1.

Lab Exercises

  • Reference links for further practice and understanding.

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Advanced Web Programming (Chapter 9) PDF

Description

Explore Chapter 9 of Advanced Web Programming, where you will dive into arrays and numbers. This chapter covers the properties of arrays, how to create and access them, along with different numerical types and mathematical functions. Prepare to enhance your programming skills with practical examples and deeper insights into handling data efficiently.

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