PWAs should be discoverable, installable, linkable, network independent, progressive, re-engageable, responsive, and safe. Progressive Web Apps are web apps that use emerging web browser APIs and features along with traditional progressive enhancement strategy to bring a native app-like user experience to cross-platform web applications. Progressive Web Apps are a useful…

Proxy describes someone or something acting on behalf of someone else. In the computer realm, we are talking about one server acting on the behalf of another computer. Proxy If we have clients (>= 1), an intermediate web server(in this case, we call it proxy), and a server. …

A function is a subprogram designed to perform a particular task. Functions are executed when they are called. This is known as invoking a function. Functions always return a value. In JavaScript, if no return value is specified, the function will return undefined. Functions are objects. …

Object.freeze() Object.freeze takes an object as an argument. Note that it modifies the object you pass as an argument. It does not copy the object and create a new one. So what does it mean for the object? You can’t add new properties to the object You can’t modify the properties…

Higher-order function is a general concept that applies to many programming languages, including JavaScript. Higher-order components (HOC) are a very similar concept. Instead of working with functions as input parameters and return values, HOCs are working with components. Higher-order functions are regular functions that do one or both of the…

Currying is an advanced technique of working with functions. It’s used not only in JavaScript but in other languages as well. Currying is a transformation of functions that translates a function from callable as f(a, b, c) into callable as f(a)(b)(c). Currying doesn’t call a function. It just transforms it. Curried functions are higher-order functions that allow us to create specialized versions of original functions. Currying works thanks to closures, which retain the enclosing function scopes after they have returned.

A Callback function is a function passed into another function as an argument, which is then invoked inside the outer function to complete some kind of routine or action. Here is a quick example: The above example is the synchronous callback, as it is executed immediately. Note, however, that callbacks are often used to continue code execution after an asynchronous operation has completed — these are called asynchronous callbacks. A good example is the callback functions executed inside a .then() block chained onto the end of a promise after that promise fulfills or rejects. This structure is used in many modern web APIs, such as fetch().

A service worker is a script that your browser runs in the background, separate from a web page, opening the door to features that don’t need a web page or user interaction. Today, they already include features like push notifications and background sync. In the future, service workers might support…

Tree shaking is a form of dead code elimination. The term was popularized by Rollup, but the concept of dead code elimination has existed for some time. The concept has also found purchase in webpack. The term “tree shaking” comes from the mental model of your application and its dependencies…