JavaScript Fundamentals for Students

What is a variable in JavaScript?

• A variable in JavaScript is a named container for storing data values.

• A variable in JavaScript is a method for defining classes.

• A variable in JavaScript is a function that performs calculations.

• A variable in JavaScript is a type of loop used for iteration.

Which of the following is a valid way to declare a variable?

• let x = 5;

• x = 5;

• const x : 5;

• var x = 5;

What are the different data types in JavaScript?

• string, number, boolean, null, undefined, symbol, object

• array, function, set

• date, time, list

• integer, float, character

How do you convert a string to a number in JavaScript?

• Apply Math.round(string)

• Convert using toString(string)

• Use stringToNumber(string) method

• Use Number(string), parseInt(string), or parseFloat(string) to convert a string to a number.

What is the purpose of a function in JavaScript?

• To store data in variables

• The purpose of a function in JavaScript is to encapsulate code for reuse and to perform specific tasks.

• To define global variables

• To create HTML elements

What is the difference between function declaration and function expression?

• Function expression can be called before its definition.

• Function declaration can only be used in strict mode.

• Function declaration is hoisted and can be called before its definition, while function expression is not hoisted and must be defined before it can be called.

• Function declaration and function expression are the same.

What is scope in JavaScript?

• Scope is the method of error handling in JavaScript.

• Scope is a type of JavaScript function.

• Scope refers to the speed of JavaScript execution.

• Scope in JavaScript defines the visibility and lifetime of variables and functions.

How can you access a variable defined in an outer function from an inner function?

• You must declare the outer variable as global to access it in the inner function.

• You can reference the outer variable directly by its name in the inner function.

• You can only access the outer variable by passing it as an argument.

• Inner functions cannot access outer variables at all.

What does DOM stand for in web development?

• Data Object Model

• Document Object Module

• Dynamic Object Model

• Document Object Model

How do you select an element by its ID in JavaScript?

• document.getElementById('yourElementId');

• getElementById('yourElementId');

• document.selectById('yourElementId');

• document.getElement('yourElementId');