How to Read Object Array In Javascript

I have an object array in Javascript but it kept showing as undefined when I try to fetch a specific value.

May I know how can I read the values in the array?

Thank you.

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function approveOrRejectTRF(primaryControl) {
    'use strict';
    if (!primaryControl) { return; }
    var formContext = primaryControl;
    var Id = formContext.data.entity.getId();

    var pageInput = {
        pageType: "webresource",
        webresourceName: "hsl_/html/TravelRequest/ApproveRejectButtonHtml.html",
        data: "&EntityId=" + Id
    };
    var navigationOptions = {
        target: 2,
        width: 800,
        height: 450,
        position: 1,
        title: "Approve/Reject"
    };
    Xrm.Navigation.navigateTo(pageInput, navigationOptions).then(
        function success(returnValue) {
            console.log(returnValue);
            console.log("Action : " + returnValue[0].actionVal);
            console.log("Comments : " + returnValue[0].commentsVal);
        },
        function error(e){
            // Handle errors
        }
    );
}

Edit: Debugger screenshot:
enter image description here