random-ip-from-subnet ==> Produces a crudely random IP address from a given subnet.

random-ip-from-subnet.js

function getIPFromSubnet(subnetRange) {

    // subnetRange = "10.0.0.0/24"
    const subnet = subnetRange.split('/')[0]; // 10.0.0.0
    const mask = subnetRange.split('/')[1]; // 24
    const ipArray = subnet.split('.'); //["10", "0", "0", "0"]


    var ipInBinary = ""; // will contain the binary equivalent of the iP

    // for each element in the array, convert from decimal to binary
    for (let quad of ipArray) {
        let octet = parseInt(quad, 10).toString(2)

        // we need each octet to be 8 bits. So provide padding for those which are less than 8 bits
        // 0101 becomes 00000101
        let octetLength = octet.length
        if (octetLength < 8) {
            let octDiff = 8 - octetLength;
            octet = "0".repeat(octDiff) + octet
        }
        
        // concat all the octets into a 32 bit binary
        ipInBinary = ipInBinary.concat(octet)          // 00001010000000000000000000000000

    }
    // console.log("ipInBinary: ", ipInBinary);

    // strip the subnet from the entire address:
    let subnetBinary = ipInBinary.slice(0, mask)    // 000010100000000000000000
    let hostsBinary = ipInBinary.slice(mask, ipInBinary.length) // 00000000


	var randomBinarySubstitute = "";
	const randomPool = "10101010101010101010101010101010"	//fix this nonsense later.
  
	for(let i=0; i<32-mask; i++){
    	randomBinarySubstitute += randomPool[Math.floor(Math.random() * ipInBinary.length)]
    }
    

    let newIPBinary = subnetBinary + randomBinarySubstitute; 

    let  finalIP = "";
    
    // split the 32 bit binary IP into an array of 8 bits, each representing an octate
    let  finalIPArray_binary = newIPBinary.match(/.{8}/g) //  ["00001010", "00000000", "00000000", "10001010"]

    // convert the binary quad array to decimal dotted quad
    for (let element of finalIPArray_binary) {
        finalIP = finalIP + "." + parseInt(element, 2);
        finalIP = finalIP.replace(/^\./, "");   // remnove the leading .
    }
    console.log("FinalIP" , finalIP)
    return finalIP
}

getIPFromSubnet('10.0.0.0/16')