JavaScript for non-developers: a primer

• A. Styling web pages
• B. Adding interactivity to web pages ✓
• C. Storing data on a server
• D. Creating databases

Why: JavaScript is primarily used to add interactivity and dynamic behavior to web pages.

• A. 2variable
• B. variable-name ✓
• C. variable name
• D. var

Why: Variable names must start with a letter, underscore, or dollar sign, and cannot contain hyphens.

• A. It displays a message in a dialog box
• B. It logs a message to the browser console ✓
• C. It changes the background color of a webpage
• D. It plays a sound

Why: console.log() is used to print messages to the browser console for debugging purposes.

• A. = ✓
• B. +
• C. -
• D. *

Why: The equals sign (=) is used to assign a value to a variable in JavaScript.

• A. function myFunction() { ... } ✓
• B. myFunction() { ... }
• C. function: myFunction() { ... }
• D. def myFunction() { ... }

Why: The correct syntax to declare a function in JavaScript is 'function myFunction() { ... }'.

• A. var myVar = 10; ✓
• B. var myVar = 10;
• C. myVar = 10;
• D. variable myVar = 10;

Why: Variables in JavaScript are declared using the var, let, or const keywords. The correct syntax is var myVar = 10;.

• A. Integer
• B. String ✓
• C. Float
• D. Decimal

Why: JavaScript has several data types, including String, Number, Boolean, Null, Undefined, and more. Integer and Float are not specific data types in JavaScript.

• A. 10
• B. 55 ✓
• C. Error
• D. NaN

Why: When a number is added to a string, JavaScript converts the number to a string and concatenates them, resulting in '55'.

• A. var
• B. let
• C. const ✓
• D. constant

Why: The const keyword is used to declare a constant in JavaScript, which cannot be reassigned after initialization.

• A. // This is a comment ✓
• B. /* This is a comment */
• C. -- This is a comment
• D. # This is a comment

Why: In JavaScript, single-line comments are written using //, and multi-line comments are written using /* ... */.

• A. A variable that stores data
• B. A block of code that performs a specific task ✓
• C. A type of loop
• D. A way to declare a class

Why: A function is a block of code that performs a specific task when called.

• A. Using the function keyword ✓
• B. Using the var keyword
• C. Using the let keyword
• D. Using the const keyword

Why: In JavaScript, functions are defined using the function keyword followed by the function name and parentheses.

• A. functionName() ✓
• B. functionName
• C. function functionName()
• D. functionName: value

Why: To call a function, you use the function name followed by parentheses.

• A. To declare variables outside the function
• B. To pass values into the function ✓
• C. To return a value from the function
• D. To define the function name

Why: Parameters are used to pass values into a function when it is called.

• A. It ends the function execution and sends a value back ✓
• B. It declares a variable inside the function
• C. It starts a loop inside the function
• D. It prints a message to the console

Why: The return statement is used to exit a function and optionally return a value to the caller.

• A. A collection of key-value pairs
• B. A list of values stored in a single variable ✓
• C. A function that performs a specific task
• D. A data type that represents true or false

Why: An array is a list of values stored in a single variable, indexed by numerical positions.

• A. fruits[2] ✓
• B. fruits(3)
• C. fruits[3]
• D. fruits.third

Why: Arrays are zero-indexed, so the third element is at index 2.

• A. let person = [name: 'John', age: 30];
• B. let person = {name: 'John', age: 30}; ✓
• C. let person = (name: 'John', age: 30);
• D. let person = <name: 'John', age: 30>

Why: Objects in JavaScript are declared using curly braces {} with key-value pairs.

• A. It removes the last element from the array
• B. It adds the number 4 to the end of the array ✓
• C. It replaces the first element with 4
• D. It inserts 4 at the beginning of the array

Why: The push() method adds one or more elements to the end of an array.

• A. pop() ✓
• B. shift()
• C. unshift()
• D. splice()

Why: The pop() method removes the last element from an array and returns that element.

• A. onmouseover
• B. onclick ✓
• C. onchange
• D. onload

Why: The onclick event is triggered when a user clicks on an HTML element.

• A. document.getElementById("inputId").value
• B. document.getElementById("inputId")
• C. document.querySelector("input").value
• D. Both A and C ✓

Why: Both methods can be used to get the value of an input field.

• A. Triggers when a form is submitted ✓
• B. Triggers when a button is clicked
• C. Triggers when a page is loaded
• D. Triggers when an input field changes

Why: The 'onsubmit' event is triggered when a form is submitted.

• A. onmouseover
• B. onclick
• C. onalert ✓
• D. onchange

Why: 'onalert' is not a valid event handler in JavaScript.

• A. To stop the default action of an event ✓
• B. To trigger an event
• C. To remove an event listener
• D. To log an event to the console

Why: The 'event.preventDefault()' method is used to stop the default action of an event.

• A. Document Object Model ✓
• B. Dynamic Object Management
• C. Data Object Manipulation
• D. Digital Operating Module

Why: DOM stands for Document Object Model, which represents the structure of HTML documents as a tree of objects.

• A. document.querySelector()
• B. document.getElementById() ✓
• C. document.getElementsByClassName()
• D. document.getElementsByName()

Why: document.getElementById() is the correct method to select an element by its ID in the DOM.

• A. innerHTML
• B. textContent
• C. innerText
• D. All of the above ✓

Why: innerHTML, textContent, and innerText can all be used to change the content of an HTML element, though they have slight differences in behavior.

• A. To change the HTML structure
• B. To modify the CSS styles of an element ✓
• C. To add new elements to the DOM
• D. To remove elements from the DOM

Why: The 'style' property is used to modify the CSS styles of an element directly in the DOM.

• A. document.createElement() ✓
• B. document.createNode()
• C. document.addHTML()
• D. document.newElement()

Why: document.createElement() is the correct method to create a new element, which can then be added to the DOM.

• A. To declare variables
• B. To display information in the browser console for debugging ✓
• C. To perform mathematical calculations
• D. To style web pages

Why: console.log() is used to print messages to the browser console, which helps developers debug their code by showing the current state of variables and program flow.

• A. Using uppercase letters
• B. Forgetting to declare a variable ✓
• C. Using numbers as variable names
• D. Adding comments to the code

Why: Forgetting to declare a variable can lead to unexpected behavior or errors, especially in strict mode, as the variable may be treated as a global variable or cause a ReferenceError.

• A. The variable was declared but not used
• B. The variable is being used before it is declared
• C. The variable is not declared anywhere in the code ✓
• D. The variable is declared but has no value

Why: A ReferenceError occurs when a variable is used in the code but has not been declared anywhere, making it inaccessible to the JavaScript engine.

• A. var myVar
• B. myVar = 10
• C. Both A and B ✓
• D. Neither A nor B

Why: In JavaScript, you can declare a variable using 'var' or assign a value to a variable without using 'var', though the latter is not considered good practice in modern JavaScript.

• A. To write faster code
• B. To find and fix errors in the code ✓
• C. To make the code look better
• D. To increase the size of the code

Why: Debugging is the process of identifying and resolving errors or bugs in the code to ensure it runs as intended.