Validate Business Process Flow using Javascript in ms crm

function AddStageHandlers() {

    Xrm.Page.data.process.addOnStageChange(StageChangedHandler);
}

function StageChangedHandler() {
    var activeStage = Xrm.Page.data.process.getActiveStage();
    var stageid = Xrm.Page.getAttribute("stageid").getValue();
    var peocessid = Xrm.Page.getAttribute("processid").getValue();
    var stageName = activeStage.getName();
    if (stageName == "BPF Stage Name") {
        if (Xrm.Page.getAttribute("optionsetattributename").getText() == "Yes") {
            if (Xrm.Page.getAttribute("attributename").getValue() == null) {
                //Previous stage ID
                Xrm.Page.data.process.movePrevious(function () { Xrm.Page.data.process.setActiveStage('stageid'); alert("All fields are Mandatory"); });
            }
            else {
                //Next stage ID
                Xrm.Page.data.process.moveNext(function () {

                     Xrm.Page.data.process.setActiveStage('stageid'); 

                    alert("All fields are Mandatory"); });
            }
        }

        else {
            //Next stage ID
            Xrm.Page.data.process.moveNext(function () { 

            Xrm.Page.data.process.setActiveStage('stageid'); 

            alert("All fields are Mandatory"); });
        }
    };
}