JavaScript – Prevent Save - Model Driven App

function onSave(executionContext)
 {
    var formContext = executionContext.getFormContext();
    var errorId = "error";
    var eventArgs = executionContext.getEventArgs();
    //To see the Save Mode return value in your browser console
    console.log("Save Mode = " + eventArgs.getSaveMode());
    //If save mode is 'Save and Close' or 'Auto Save', inhibit default behavior i.e. save
    if (eventArgs.getSaveMode() == 2 || eventArgs.getSaveMode() == 70 || eventArgs.getSaveMode() == 1) {
        var productObj = formContext.getAttribute("product").getValue();
        var assetObj = formContext.getAttribute("customerasset").getValue();
        if (productObj == null && assetObj == null) {
            eventArgs.preventDefault();
            formContext.ui.setFormNotification("Product or Customer Asset must be provided", "ERROR", errorId);
        }
        else
        {
            formContext.ui.clearFormNotification(errorId);
        }
    }
    //To see if the auto save behavior was prevented in your browser console
    console.log("Default behaviour prevented: " + eventArgs.isDefaultPrevented());
  }