JSFiddle - React, Tailwind, and code Playground

HTML

<div id="log">

</div>

JavaScript

let a = 10;

function parent(){
	let a = 2;
	neighbor();
	let child = function(){
		a++;
    document.getElementById("log").innerHTML += 'child(a): ' + a + '<br>';
		//alert('child(a): ' + a);
	}
	return child;
}

function neighbor(){
	document.getElementById("log").innerHTML += 'neighbor(a): ' + a + '<br>';
	//alert('neighbor(a): '+a++);
}


let result=  parent();
result();
result();
result();
result();
result();