Create Nested Functions In JavaScript

In JavaScript, a function declaration defines a function with the specified parameters and code block.

Functions can be called before their creation due to hoisting. A JavaScript function is a subprogram that can be called by code externally or internally to the function. Nested functions are defined within other functions.

Nested functions have access to the variables of their parent function.

Common Syntax Of Nested Functions In JavaScript

Glossary:

Hoisting

The interpreter moves function declaration to the top of their scope.

Scope

The accessibility of variables and functions within certain parts of your code.

Declaration

Used to define variables, functions, and constants.

Method

Function defined within a object.

Arrow Functions

Syntax for creating anonymous expressions.

Closures

Access variables from outer scope even after outer function has finished.

Common Nested Functions

Ojamboshop.com Learning JavaScript Nested Functions

Name	Description	Example
function one() {function two() {}}	Nested Function.	function one() {function two() {}}
myFunc()	Closure	let m = myFunc();
Name	Description	Example

JavaScript Nested Functions Snippet

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// OjamboShop.com Learning JavaScript Nested Functions Tutorial

// Nested Function
function outFunc() {
	let name = 'John';
	function inFunc() {
		console.log('The name is ' +name);
	}
	inFunc();
}
outFunc();

// Closure
function showName() {
	let name = 'Jane';
	function displayName() {
		console.log(name);
	}
	return displayName;
}
let myFunc = showName();
myFunc();

// Closure Arguments
function addTwo(num1) {
	return function(num2) {
		return num1+num2;
	}
}
let myClosure = addTwo(5);
console.log(myClosure(3));

// IIFE Arrow Function Closure
let calculateSum = (function(num1, num2) {
	let sum = 0;
	return function() {
		sum = num1+num2;
		return sum;
	}
})(5,3);
calculateSum();

Usage

You can use any IDE or text editor and the web browser to compile and execute JavaScript code. For this tutorial, the OjamboShop.com Learning JavaScript Course Web IDE can used to input and compile JavaScript code for the nested functions.

Open Source

JavaScript follows the ECMAScript standard and is licensed under the W3C Software License by web browser vendors and runtime environment vendors. This allows commercial use, modification, distribution, and allows making derivatives proprietary.

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Conclusion:

JavaScript makes it easy to use create nested functions. Define functions within other functions in order to access variables of their parent function.

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References:

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• Learning Python Ebook on Amazon
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