<p>Do a prime number search from <input id="from" value="1"> to <input id="to" value="2000000" size="100">.</p>
<button onclick="doSearch()" id="searchButton">Start Searching</button>
<button onclick="cancelSearch()">Cancel</button>
<div id="primeContainer">
</div>
<div id="status"></div>
<script id="FindPrimes" type="javascript/worker">
onmessage = function(event) {
var primes = findPrimes(event.data.from, event.data.to);
postMessage(
{messageType: "PrimeList", data: primes}
);
};
function findPrimes(fromNumber, toNumber) {
// Create an array containing all integers between the two specified numbers.
var list = [];
for (var i=fromNumber; i<=toNumber; i++) {
if (i>1) list.push(i);
}
// Test for primes.
var maxDiv = Math.round(Math.sqrt(toNumber));
var primes = [];
var previousProgress;
for (var i=0; i<list.length; i++) {
var failed = false;
for (var j=2; j<=maxDiv; j++) {
if ((list[i] != j) && (list[i] % j == 0)) {
failed = true;
} else if ((j==maxDiv) && (failed == false)) {
primes.push(list[i]);
}
}
// Give a progress update.
var progress = Math.round(i/list.length*100);
if (progress != previousProgress) {
postMessage(
{messageType: "Progress", data: progress}
);
previousProgress = progress;
}
}
return primes;
}
</script>
body {
font-family: "Lucida Sans Unicode", "Lucida Grande", sans-serif;
margin: 20px;
}
#primeContainer {
border: solid 1px black;
padding: 3px;
height: 300px;
max-width: 500px;
overflow: scroll;
overflow-x: hidden;
font-size: x-small;
margin-top: 20px;
margin-bottom: 10px;
}
input {
width: 80px;
}
button {
padding: 3px;
}
p {
margin-bottom: 3px;
}
#status {
color: darkred;
}
var statusDisplay;
var worker;
var searchButton;
window.onload = function() {
statusDisplay = document.getElementById("status");
searchButton = document.getElementById("searchButton");
};
function doSearch() {
// Get the two numbers in the text boxes. This is the search range.
searchButton.disabled = true;
var fromNumber = document.getElementById("from").value;
var toNumber = document.getElementById("to").value;
// Ordinarily you would give the web worker JavaScript in a separate
// file, using a line of code like this.
//worker = new Worker("PrimeWorker.js");
// Because this example is hosted on CodePen,
// which doesn't let you use separate JS files,
// we need to use a workaround to grab the
// PrimeWorker.js code from the findPrimes() function
// on this page.
var blob = new Blob([document.querySelector('#FindPrimes').textContent]);
blobURL = window.URL.createObjectURL(blob);
worker = new Worker(blobURL);
worker.onmessage = receivedWorkerMessage;
worker.onerror = workerError;
worker.postMessage(
{ from: fromNumber,
to: toNumber
}
);
statusDisplay.innerHTML = "A web worker is on the job ("+
fromNumber + " to " + toNumber + ") ...";
}
function receivedWorkerMessage(event) {
var message = event.data;
if (message.messageType == "PrimeList") {
var primes = message.data;
// Show the prime number list on the page.
var primeList = "";
for (var i=0; i<primes.length; i++) {
primeList += primes[i];
if (i != primes.length-1) primeList += ", ";
}
var displayList = document.getElementById("primeContainer");
displayList.innerHTML = primeList;
if (primeList.length == 0) {
statusDisplay.innerHTML = "Search failed to find any results.";
}
else {
statusDisplay.innerHTML = "The results are here!";
}
searchButton.disabled = false;
}
else if (message.messageType == "Progress") {
statusDisplay.innerHTML = message.data + "% done ...";
}
}
function workerError(error) {
statusDisplay.innerHTML = error.message;
}
function cancelSearch() {
worker.terminate();
worker = null;
statusDisplay.innerHTML = "Search cancelled.";
searchButton.disabled = false;
}
This Pen doesn't use any external CSS resources.