var myRequest = req.body
console.log(myRequest)

{
    "methodcall": {
        "methodname": ["userLogin"],
        "params": [{
            "param": [{
                "value": [{
                    "string": ["test1"]
                }]
            }, {
                "value": [{
                    "string": ["password"]
                }]
            }]
        }]
    }
}

var username = myRequest.methodcall.params.param...first value string
var password = myRequest.methodcall.params.param...second value string