json={ 
     "ShareRecords": [],
        "RecordOwnership": {
            "Ownerofrecord": "false"
        },
        "QueryDetails": {
            "UserName": "Wendy West",
            "ObjectName": "SBQQ__Quote__c"
        },
        "ProfileSystemPermissions": {
            "ViewAllData": "false",
            "ProfileSystemPermissionId": "0PS5w000002S7qAGAS",
            "ProfileName": "*Sales",
            "ModifyAllData": "false",
            "hasAccess": "NoAccess"
        },
        "ProfileObjectPermissions": [
            {
                "ViewAllRecords": "true",
                "ProfileObjectPermissionId": "1105w00001Pw2xmAAB",
                "PermissionRead": "true",
                "PermissionName": "X00eo0000000f9DDAAY",
                "PermissionEdit": "true",
                "PermissionDelete": "true",
                "PermissionCreate": "true",
                "ModifyAllRecords": "true",
                "hasAccess": "FullAccess"
            }
        ],
        "PlatformFinalComputedAccess": {
            "MaxAccessLevel": "All",
            "HasTransferAccess": "true",
            "HasReadAccess": "true",
            "HasEditAccess": "true",
            "HasDeleteAccess": "true",
            "HasAllAccess": "true"
        },
        "PermissionSetSystemPermissions": [
            {
                "ViewAllData": "false",
                "PermissionSetSystemPermissionId": "0PS5w000002S7qAGAS",
                "PermissionSetName": "X00eo0000000f9DDAAY",
                "ModifyAllData": "false",
                "hasAccess": "NoAccess"
            },
            {
                "ViewAllData": "false",
                "PermissionSetSystemPermissionId": "0PS5w000002S7rtGAC",
                "PermissionSetName": "Pardot",
                "ModifyAllData": "false",
                "hasAccess": "NoAccess"
            },
            {
                "ViewAllData": "false",
                "PermissionSetSystemPermissionId": "0PS5w000002S7sYGAS",
                "PermissionSetName": "Sales_Cloud_Einstein_PSL",
                "ModifyAllData": "false",
                "hasAccess": "NoAccess"
            },
            {
                "ViewAllData": "false",
                "PermissionSetSystemPermissionId": "0PS5w000002S7t4GAC",
                "PermissionSetName": "EinsteinAnalyticsPlusUserPSL",
                "ModifyAllData": "false",
                "hasAccess": "NoAccess"
            },
            {
                "ViewAllData": "false",
                "PermissionSetSystemPermissionId": "0PS5w000002S7tDGAS",
                "PermissionSetName": "Motivate_Standard_User",
                "ModifyAllData": "false",
                "hasAccess": "NoAccess"
            },
            {
                "ViewAllData": "false",
                "PermissionSetSystemPermissionId": "0PS5w000002S7tEGAS",
                "PermissionSetName": "Align_Standard_User",
                "ModifyAllData": "false",
                "hasAccess": "NoAccess"
            },
            {
                "ViewAllData": "false",
                "PermissionSetSystemPermissionId": "0PS5w000002S7tFGAS",
                "PermissionSetName": "Perform_Standard_User",
                "ModifyAllData": "false",
                "hasAccess": "NoAccess"
            },
            {
                "ViewAllData": "false",
                "PermissionSetSystemPermissionId": "0PS5w000002S7tKGAS",
                "PermissionSetName": "Lightning_Dialer",
                "ModifyAllData": "false",
                "hasAccess": "NoAccess"
            }
        ],
        "PermissionSetObjectPermissions": [
            {
                "ViewAllRecords": "true",
                "PermissionSetObjectPermissionId": null,
                "PermissionRead": "true",
                "PermissionName": "X00eo0000000f9DDAAY",
                "PermissionEdit": "true",
                "PermissionDelete": "true",
                "PermissionCreate": "true",
                "ModifyAllRecords": "true",
                "hasAccess": "FullAccess"
            }
        ],
        "OWDAccessLevel": {
            "OWDAccessLevelId": "000000000000000AAA",
            "InternalSharingModel": "ReadWrite",
            "ExternalSharingModel": "Private"
        },
        "GroupMembership": [
            {
                "Type": "Regular",
                "Name": "SalesReps",
                "GroupId": "00G5w000007NK9CEAW"
            }
        ] 
    };

// Converting JSON object to JS object
 obj = JSON.parse(json);
 QDetails=obj.QueryDetails.UserName;
 console.log(QDetails);
 

}