A JavaScript function inside a Block Scope: Simplified

Scoping determines the visibility of a variable, an object, or a function.  For example, a variable defined inside a function is visible or can be accessed only inside that particular function.   JavaScript has 4 types of scope.  Global scopeFunctional scopeLexical ScopeBlock Scope Out of the above four scoping, Block Scoping became part of JavaScript … Continue reading A JavaScript function inside a Block Scope: Simplified

How to manually pass the value of ‘this’ object in a JavaScript function

Every JavaScript function has a ‘this’ object, and the value of ‘this’ object depends on the way you call the function. To pass the value of ‘this’ manually, you need to call the function indirectly. In JavaScript, you call a function indirectly to pass the value of ‘this’ object manually. Manually calling a function is … Continue reading How to manually pass the value of ‘this’ object in a JavaScript function

How to make a property non-enumerable in JavaScript?

By default, all the properties of JavaScript objects are enumerable. That means you can enumerate them in a for loop or read them using the Object.values(). Let us consider an object Dog as shown below, let Dog = { name :'foo', age: 9, canRun : true, eatMilk : false } You can enumerate all properties … Continue reading How to make a property non-enumerable in JavaScript?

How to merge arrays using spread operator in JavaScript?

Have you come across a requirement to merge two or more arrays  into another array? Let us say, you have two arrays as shown below, const metrocities = ['Delhi', 'Mumbai','Chennai','Bangalore','Hyderabad']; const smallcities = ['Jamshedpur','Pune','Lucknow','Trivandrum']; You need to merge them in another array with optional extra elements in the resultant array. JavaScript array spread operator makes … Continue reading How to merge arrays using spread operator in JavaScript?

How to create Private Properties in JavaScript.

We don't have Access Modifiers in JavaScript, and all properties of an object are public, which means you can read and modify them outside the object. But what if you have a requirement to create private properties?  Consider Product object as mentioned below, let Product = { id: '1', price: 200, title: 'Pencil' } console.log(Product.id); … Continue reading How to create Private Properties in JavaScript.

Explain Object.keys in JavaScript

Enumerating through the properties of a JavaScript object is a persistent requirement. Hence it becomes a popular question in a JavaScript interview. Any good JavaScript developer must know about various available options. Note: You can find a video tutorial on the same at the end of the article. To start with considering the Dog object … Continue reading Explain Object.keys in JavaScript

Five Things about JavaScript delete operator

A better understanding of delete operator is necessary for JavaScript developers. As the name suggests, the delete operator deletes properties from the object.  You can delete a property as shown below: It returns true on successful deletion. However, in some cases, it may return true even if it does not delete a property. In this … Continue reading Five Things about JavaScript delete operator

All about NaN in JavaScript

In JavaScript, NaN is one of the most confusing concepts; hence, it is often asked in the interview. You may have come across questions such as, What is NaN What is the type of NaN How to check for the NaN What is the difference between isNaN() and Number.isNaN() In this post, let us learn … Continue reading All about NaN in JavaScript

Simplifying Maps in the JavaScript

Maps is a data structure, which stores the key/value pair in an ordered way.  Since the inception of the JavaScript, objects are primarily used for the map.  Consider the below code listing:   To store two key/value pairs, we have created an object foo and using the keys such as id and color to retrieve … Continue reading Simplifying Maps in the JavaScript

Why you need Proxy objects in JavaScript

JavaScript is not truly Object Oriented language, hence implementing requirements as stated below could be challenging. For example, Throw an error if the setting value of a property does not satisfy a particular condition If the property does not exist on set some default value instead of undefined If the property does not exist on … Continue reading Why you need Proxy objects in JavaScript