Can Client-Side Javascript Perform DNS Lookups?

Exploring DNS Lookup Capabilities in Client-Side Javascript

The question arises: can client-side Javascript effectively perform DNS lookups, translating hostnames into corresponding IP addresses?

Javascript Limitations

Pure Javascript lacks this functionality. It cannot directly query DNS servers to retrieve IP addresses.

Server-Based Workarounds

To circumvent this limitation, consider leveraging a server-side script located within the client's domain. The script can output the desired IP address and be accessed via XMLHttpRequest in Javascript. However, this approach requires additional server infrastructure.

Alternate Method: JSONP Webservice

An alternative approach involves using a JSONP webservice. JSONP allows cross-domain requests by wrapping responses in a callback function. By incorporating a pre-existing webservice, such as the one provided by Google App Engine, you can obtain the client's IP address without relying on a server proxy:

<script type="application/javascript">
function getip(json) {
  alert(json.ip); // alerts the ip address
}
</script>

<script type="application/javascript" src="http://jsonip.appspot.com/?callback=getip">
</script>

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