Check out Ws.js. It is a JavaScript library that helps implement ws-security.
Personally I would only do this if I have to integrate a web client with an existing WCF service that I do not have the source code for. The overhead is too large to maintain the SOAP protocol and WCF security for a web client without any added benefit. If you control the source for this service I would provide a REST API for the web client using ASP.NET Web API and use SSL with HTTP basic security.