let fun1String = "sayHello()"
webview.stringByEvaluatingJavaScript(from: fun1String)

let fun2String = "sayHelloTo('lien')"
webview.stringByEvaluatingJavaScript(from: fun2String)

let fun3Stirng = "sayHelloWithRtnValue('lien')"
let rtnValue = webView.stringByEvaluatingJavaScript(from: fun3Stirng)
print("returned value from JavaScript: \(rtnValue)")