Conteúdo do Curso

JavaScript Data Structures

1. Introduction and Prerequisites

Introduction to JavaScript Data Structures Prerequisites for Learning JavaScript Data Structures What You'll Learn in This Course Tips for Success

2. Fundamentals of JavaScript Objects

Understanding Objects in JavaScript Creating Objects in JavaScript Working with Nested Object Properties Challenge: Create and Structure an Object Accessing Object Properties in JavaScript Challenge: Retrieve Object Property Values Managing Object Properties Challenge: Modify and Extend an Object Defining Object Methods Using Properties within Methods Challenge: Work with Object Methods Fundamentals of JavaScript Objects Sum-Up

3. Advanced Object Manipulation Techniques

Iterating Over Object Properties with the for...in Loop Challenge: Explore Object Properties with Iteration Using hasOwnProperty() to Check Object Properties Challenge: Object Property Iteration with hasOwnProperty()Cloning and Merging Objects with the Spread Operator Challenge: Combine Objects with the Spread Operator Destructuring Objects for Cleaner Code Challenge: Extract Data with Object Destructuring Advanced Object Manipulation Sum-Up

4. Mastering JavaScript Arrays

Understanding JavaScript Arrays Challenge: Access Array Elements Modifying Arrays and Accessing Elements Challenge: Modify Array Elements Iterating Over Arrays with the for Loop Challenge: Loop Through Arrays with for Using the for...of Loop for Array Iteration Challenge: Efficient Array Iteration with for...of Mastering JavaScript Arrays Sum-Up

5. Advanced Array Methods and Transformations

Transforming Arrays with the map() Method Challenge: Modify Array Elements Using map()Filtering Arrays with the filter() Method Challenge: Select Specific Data Using filter()Finding Elements in an Array with the find() Method Challenge: Search for Items Using find()Sorting Arrays with the sort() Method Challenge: Sort and Extract Data with sort()Advanced Array Methods and Transformations Sum-Up Course Summary

Using hasOwnProperty() to Check Object Properties

When iterating through an object's properties using the for...in loop, it's important to distinguish between the object's own properties and those inherited from its prototype chain.

The hasOwnProperty() method is a valuable tool for checking whether a property belongs to the object or is inherited from a prototype. Let's explore the hasOwnProperty() method and how it can safely handle object properties during iteration.

Understanding hasOwnProperty()

The hasOwnProperty() method is a built-in JavaScript method that allows us to check if a specific property exists directly on an object. It returns a Boolean value (true or false) indicating whether the object has a property with the specified name.

Here is the basic syntax of the hasOwnProperty() method:

object: The object you want to check;
property: The property name we want to check for.

Using hasOwnProperty() with for...in

Using the for...in loop, we can combine it with the hasOwnProperty() method to iterate through an object's properties. It's important to add a check for own properties at each iteration to ensure that we only access the object's own properties. Even if we are certain that the object has no inherited properties, this check will protect against future possible errors.


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const exercise = {
  name: "Deadlift",
  primaryMusclesWorked: "Erector spinae",
  equipment: "Barbell",
  exerciseType: "Strength",
  difficulty: "Intermediate",
};

for (let key in exercise) {
  if (exercise.hasOwnProperty(key)) {
    console.log(`Property: ${key}, Value: ${exercise[key]}`);
  }
}

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Seção 3. Capítulo 3

JavaScript Data Structures

Using hasOwnProperty() to Check Object Properties

Understanding hasOwnProperty()

Using hasOwnProperty() with for...in

1. What is the primary purpose of the `hasOwnProperty()` method?

2. What type of value does the `hasOwnProperty()` method return?

3. When using `hasOwnProperty()` with the `for...in` loop, why is it important to check for own properties?

4. In the code below, what will be logged when iterating through the `video` object's properties?

JavaScript Data Structures

Using hasOwnProperty() to Check Object Properties

Understanding hasOwnProperty()

Using hasOwnProperty() with for...in

1. What is the primary purpose of the hasOwnProperty() method?

2. What type of value does the hasOwnProperty() method return?

3. When using hasOwnProperty() with the for...in loop, why is it important to check for own properties?

4. In the code below, what will be logged when iterating through the video object's properties?

1. What is the primary purpose of the `hasOwnProperty()` method?

2. What type of value does the `hasOwnProperty()` method return?

3. When using `hasOwnProperty()` with the `for...in` loop, why is it important to check for own properties?

4. In the code below, what will be logged when iterating through the `video` object's properties?