JSFiddle - React, Tailwind, and code Playground

by Rey Den Nalasa

JavaScript

var num=window.prompt();
var str = num.toString();
var str_array = str.split("");

var result = [];

var i;
for(i = 0;i <= str_array.length;i++){
	//if(str_array[i]%2 === 0)
	if((str_array[i-1]%2 === 0)&&(str_array[i]%2 === 0)){
		 result.push('-', str_array[i]);
	}
	
	else{
		result.push(str_array[i]);
	}
}

console.log(result.join(''));