JSFiddle - React, Tailwind, and code Playground

JavaScript

function dot2num(dot) { // the same as ip2long in php
    var d = dot.split('.');
    return ((+d[0]) << 24) +  
           ((+d[1]) << 16) + 
           ((+d[2]) << 8) + 
            (+d[3]);
}

function num2array(num) {
     return [
        (num & 0xFF000000) >>> 24,
        (num & 0x00FF0000) >>> 16,   
        (num & 0x0000FF00) >>>  8,
        (num & 0x000000FF)
       ];    
}

function htonl(x)
{
     return dot2num(num2array(x).reverse().join('.')); 
}

var ipbyte = dot2num('12.34.56.78');
alert(ipbyte);
var inv = htonl(ipbyte);
alert(inv + '=' + num2array(inv).join('.'));