Creating an Object in JavaScript 

JavaScript was created using a simple object-based paradigm. An object is a collection of properties. A property can have a function as its value, which is referred to as a method. Like many other programming languages, JavaScript’s objects are comparable to actual physical objects. An object in JavaScript is a separate entity having properties and a type. 

Consider comparing it to a cup. A cup is an item with characteristics. A cup has shape, weight, colour, material, and other characteristics. Similarly, JavaScript objects can have properties that specify their attributes.   

How to Create an Object in JavaScript  

Objects are an important part of the JavaScript language, and there are two ways that you can create them. 

New Keyword  

The first way is by using the new keyword, which creates a new empty object. The new keyword works like this: you give it a variable name, optionally followed by arguments to initialise its properties.

Example:

var x = new Number(5);. 

The variable x now contains an object with all five properties initialised to 5.

Object Constructor  

The second way is by using the Object() constructor function, which returns an instance of the built-in Object class.  

If you want your object (or any other value) to act like a regular variable, you need to assign its values and then initialise its properties (and, optionally, its methods).

Let’s say you want to create an object in JavaScript. 

The first thing you have to do is create a variable of type Object. Then, you can assign values to that variable. 

Example: 

For example, this code creates a variable called myObject and assigns it the value of “Hello”.

var myObject = {};
myObject.name = "Hello";

There are many ways to do this. One way is to use the Array.map function: 

Object to Array JavaScript

Various types of methods can be used in JavaScript to turn an object into an array. Object.keys(), Object.values(), and Object.entries are a few of the available methods ().

Example:

var map = function(obj, f) 
{ 
return Object.keys(obj).map(f); 
} 

The object we’re mapping is the object returned by obj, and f is a function that takes one argument (an object) and returns another object. We’ll call this new object “result”.

To create an object in JavaScript, you need to use the new keyword.

Using a New Keyword to Create an Object in the JavaScript   

When using a new keyword to create an object in JavaScript, you can use the following codes:

function Person(name)  
{ this.name = name; } Person.prototype = { getName: function() { return this.name; }, sayHello: function() { console.log("hello"); } }; var p = new Person("Jack"); p.sayHello();
function findIndexOfObject(arr, obj) { for (var i = arr.length; i--;) if (arr[i] == obj) return i; return -1 }

You can also use a for-in loop to iterate over all elements of arr:

function findIndexOfObject(arr, obj) { for (var i = 0; i < arr.length; i++) if (arr[i] == obj) return i; return -1 } 

The above code creates a new object called p, which contains an attribute named name and a method called sayHello(). 

You can also create several objects at once using the new keyword: 

var p = new Person("Jack"); var q = new Person("Rose"); q.sayHello();

The above code will create two objects, one with the name “Jack” and another with the name “Rose.”

Finding the Index of an Object 

In JavaScript, there are many ways to find an index of an object in an array. But the best way is using for..of loop. 

The syntax for for..of loop is:  

for (const [index, ...array]) { // Do something with the array }

This loop will iterate over each element of the array and assign it to a variable called index. You can use another variable name if you want. For example, if we have [1, 2] as input and want to print its length value, then we can do this:

for (const index of [1, 2]) { console.log(index); }

Note that we have used the const keyword here so that we cannot modify the values inside for..of loop. If you try modifying any value inside for..of loop, then it will throw an error message saying “ReferenceError: Array has no method ‘indexOf'” which means that there is no such function named indexOf .

In JavaScript, it’s easy to find the index of an element in an array. We can use the built-in Array.prototype.indexOf() method.

Example:

The following code is a simple example that shows how we can get the index of an element in an array using this method:

var arr = [1, 2, 3];
arr.indexOf(2); // returns 0
arr.indexOf(4); // returns 1
arr.indexOf(5); // returns 2
arr[0]; // returns 3
arr[1]; // returns 4

The indexOf() method returns the position of an item in a collection or -1 if it isn’t found.

The indexOf() method is used to find an object or array element in a collection. It searches for an item within another collection and returns the position of that item within the collection.

How to Check Code in an Array?

Use the following code to check whether a given number exists in an array:

var people = [ {name: "John", age: 27}, {name: "Mary", age: 36}, {name: "Jerry", age: 33} ];

Assume that you want to check whether two numbers are equal or not. You can do this by using the following code:

var people = [ {name: "John", age: 27}, {name: "Mary", age: 36}, {name: "Jerry", age: 33} ]; console.log(people[0].age === people[2].age);

 For example, if your array contains [‘John’, ‘Mary’, ‘Jerry’], then the expression would return true because ‘John’ and ‘Jerry’ are equal in terms of their ages. 

When creating objects with this method, it’s important to remember that they have no methods or properties until after they’ve been created (at least in CommonJS). This means that they can’t be used as arguments to any function or as keys in an array or hash. You also can’t use them as if they were regular variables—they’re not actually variables but rather objects.

5 Day Coding Challenge – learn JavaScript basics

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