What is Functions?
Functions is a JavaScript concept that provides a way to group code into functional units. It’s comprised of three parts: the function keyword, the name of the function, and an optional list of parameters and their associated values.
Functions allow programmers to reuse code across different parts of a program. They also allow for modular programming because code can be broken down into smaller units that are easier to manage and reason about than an entire program.
They can be used to organize code and make it easier to read and maintain. Functions are one of the most important features of JavaScript and they are called by using the function name followed by parentheses and a list of parameters enclosed by parentheses.
How to declare Functions in JavaScript?
A function is declared with the keyword function followed by the name of the function, then parentheses and an opening parenthesis, then comma-separated parameters in the parentheses, then an opening bracket and closing parenthesis, which creates the body of the function.
A function can also be called by using this keyword followed by parentheses containing parameters enclosed in curly braces {}.
Types of Functions in JavaScript?
Functions are the key building blocks of JavaScript. There are many different kinds of Functions in JavaScript. This article highlights the most important types of Functions in JavaScript and how they work.
The types of functions mentioned here are:
The Function constructor:
The Function constructor in JavaScript is a utility function that is used to create a function. It takes a single argument, which is the function’s name, and returns the function as an object. The Function constructor in JavaScript is most commonly found in the context of ES6 or ECMAScript 2015 specifications. The Function constructor is a JavaScript object that contains a method called `call` which is used to execute functions.
Anonymous functions:
Anonymous functions are functions that are not associated with a name. This is the default function and is used when the function does not need to be associated with a specific name.
Anonymous functions can only be identified by the parentheses following it and cannot be referenced in your code. Anonymous functions are often used for utility purposes that don’t need to have a name or an identifier attached to it.
The anonymous function takes input parameters and assigns them to supplied variables, then executes some task in your program’s code, or simply returns a result without any special handling of an error or return value.
Anonymous functions are also used for event handling. When we assign an event handler to an anonymous function, it will be executed when the event occurs. This can be done with either a click or mouseover event on DOM element objects.
Lexical scope:
The lexical scope is a way to set the visibility of variables and properties in JavaScript. Variables and properties that are not declared private are visible to all code blocks.
In JavaScript, the lexical scope is a way to set the visibility of variables and properties. This can be helpful in cases where you want one function to access a variable from another function without worrying about what function it’s coming from. Let’s take an example:
function add(x) {
var y = x+1;
}
add(2); // this will print “3”
add(5); // this will print “7”
Function parameter:
A Function in JavaScript is an executable block of code that can take parameters and return a value. It can be created using the function keyword or by calling the Function constructor directly.
Scope chain:
Scope chain is a concept in JavaScript that gives an inheritance mechanism to objects.
If you have a function called myFunction, and you invoke it once, then the function will create a new scope for its arguments. When you invoke the function again, you will use the same scope as before. This can make your code easy to read and maintain.
The Scope chain is also used by a lot of libraries to provide options that are not accessible on specific objects.
