Podcast
Questions and Answers
What is the main reason for avoiding the use of constructors for primitive types in JavaScript?
What is the main reason for avoiding the use of constructors for primitive types in JavaScript?
- Constructors are only allowed for complex data structures.
- Using constructors automatically makes all properties static.
- It can lead to unexpected behavior due to object instances. (correct)
- Primitive values are less efficient than object instances.
Which of the following represents the best practice for creating a plain object in JavaScript?
Which of the following represents the best practice for creating a plain object in JavaScript?
- let obj = Object.assign({}, {});
- let obj = {}; (correct)
- let obj = new Object();
- let obj = Object.create(null);
If a developer uses 'new String("banana")', what type will the value be considered in JavaScript?
If a developer uses 'new String("banana")', what type will the value be considered in JavaScript?
- String object (correct)
- String reference
- String literal
- String primitive
What advantage does using primitive values over object instances provide in JavaScript?
What advantage does using primitive values over object instances provide in JavaScript?
What is the main purpose of the Math object in JavaScript?
What is the main purpose of the Math object in JavaScript?
What is true about constructor functions in JavaScript?
What is true about constructor functions in JavaScript?
Which of the following best describes primitive values in JavaScript?
Which of the following best describes primitive values in JavaScript?
What happens when you compare two String objects in JavaScript?
What happens when you compare two String objects in JavaScript?
When creating an instance of the Icecream object, which method is invoked?
When creating an instance of the Icecream object, which method is invoked?
Which of the following demonstrates the correct way to create a new array?
Which of the following demonstrates the correct way to create a new array?
What is a unique characteristic of object instances created with constructors?
What is a unique characteristic of object instances created with constructors?
In what scenario is using a constructor function preferable to using primitive values?
In what scenario is using a constructor function preferable to using primitive values?
Flashcards
Built-in JavaScript Objects
Built-in JavaScript Objects
Pre-defined objects in JavaScript with specific functionalities, like Math, Date, Array, and Functions.
Math Object
Math Object
A built-in object providing math constants and functions (like squaring).
Date Object
Date Object
Used to work with dates and times.
Array
Array
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Constructor Function
Constructor Function
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Primitive Value
Primitive Value
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Object Instance
Object Instance
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Performance (Primitive vs. Object)
Performance (Primitive vs. Object)
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Primitive values in JS
Primitive values in JS
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Object literal syntax
Object literal syntax
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Avoid new String() for strings
Avoid new String() for strings
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Why use primitive values
Why use primitive values
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Object Literal syntax vrs new Object()
Object Literal syntax vrs new Object()
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Study Notes
Built-in Object Types
- Math: A static object providing mathematical constants and functions. Example:
Math.pow(2, 5)returns 32. - Date: An object for working with dates and times. Creating a
Dateobject:new Date(). - Array: Stores multiple values in one variable. Created using array literal syntax
[]ornew Array(). - Function: A first-class object in JavaScript. Defined using function literal syntax (e.g.,
() => {}) or the Function constructor.
Constructor Functions
- Creating Instances: Using the
newkeyword creates instances of an object defined by a constructor function. Example:function Icecream(flavor) { this.flavor = flavor; this.meltIt = function() { console.log(`The ${this.flavor} ice cream has melted`); }; } let kiwiIcecream = new Icecream("kiwi"); - Custom Constructor Functions: Enables creation of objects tailored for specific needs.
- Primitive Values vs. Object Instances: Primitive values (strings, numbers, booleans) are basic data types, while object instances are created by constructors (e.g.,
new String()). - Performance: Primitive values generally outperform object instances for operations like comparison (e.g., comparing string literals vs. String objects).
- Best Practices:
- Avoid using constructors for primitive types (
String,Number,Boolean). Use primitives instead. - Prefer object literal syntax (
{}) overnew Object()for creating plain objects.
- Avoid using constructors for primitive types (
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Description
This quiz explores the built-in object types in JavaScript, including Math, Date, Array, and Function. It also covers constructor functions and how to create instances of objects using the 'new' keyword. Challenge your understanding of these fundamental concepts in JavaScript programming.
