Contents
Functions are one of the most important things in JavaScript. Read this blog post to find out what functions are, how they work, and why you should use them.
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Introduction
A function is a JavaScript procedure—a set of statements that performs a task or calculates a value. To use a function, you must define it somewhere in the scope from which you wish to call it.
Functions are one of the fundamental building blocks in JavaScript. You can call or invoke a function by using its name followed by parenthesis, ().
What is a Function?
A function is a block of code that performs a specific task. Functions are often “called” or “invoked” when they are needed. For example, a function can be called when an event occurs, such as when a user clicks a button. Functions can also be called from other functions. Functions can accept parameters, which are values that are passed to the function when it is called. Parameters are optional, however, and a function can be written without any parameters.
Function Declaration
A function declaration is a type of function that is declared with the keyword “function”. It consists of a function name, an optional list of parameters enclosed in parentheses, and a body containing one or more JavaScript statements. The following is an example of a function declaration:
function hello() {
console.log(‘Hello, world!’);
}
Function Expression
A function expression is a function definition that is assigned to a variable.
var add = function(a, b) {
return a + b;
};
Arrow Function
An arrow function is a shortened syntax for a function expression.
Instead of the keyword function, you use an arrow (=>). An arrow function can have either a concise body o ra block body.
If the function only has one statement in its body, you can omit the curly brackets and write everything on one line. This is called a concise body.
For example, this arrow function returns the square of a number:
“`
const square = num => num * num;
Conclusion
In conclusion, a function is a block of code that performs a specific task. Functions are declared with the keyword function and are invoked by calling them with parentheses. Functions can take arguments, which are values that are passed to the function when it is invoked. Functions can return values, which is the value that is returned to the caller when the function is finished executing. Functions can be defined inside of other functions, which are called nested functions, and they can be passed as arguments to other functions, which are called callback functions.
