How to save CSV data to SharePoint 2013 list without iterating through the each record using JavaScript/REST?

The Rest API is identical (As far as I know) between 2013 and 2013/Online. So you should be able to use this Rest endpoint:

http://site url/_api/web/lists/GetByTitle('Test')/items

Documentation for the Rest API is here: https://docs.microsoft.com/en-us/sharepoint/dev/sp-add-ins/working-with-lists-and-list-items-with-rest

I’m not very proficient in javascript, but it would seem there’s quite a few snippets you could use. Maybe this will get you started:

// occurs when a user clicks the create button
function CreateNew() {
    var listName = "MyList";
    var newItemTitle = "New Title Item";
    CreateListItemWithDetails(listName, _spPageContextInfo.webAbsoluteUrl, newItemTitle, function () {
        alert("New Item has been created successfully.");
 }, function () {
     alert("Ooops, an error occured. Please try again.");
 });
}

// CREATE Operation
// listName: The name of the list you want to get items from
// weburl: The url of the web that the list is in. 
// newItemTitle: New Item title.
// success: The function to execute if the call is sucesfull
// failure: The function to execute if the call fails
function CreateListItemWithDetails(listName, webUrl, newItemTitle, success, failure) {
    var itemType = GetItemTypeForListName(listName);
    var item = {
        "__metadata": { "type": itemType },
        "Title": newItemTitle
    };

    $.ajax({
        url: _spPageContextInfo.siteAbsoluteUrl + "/_api/web/lists/getbytitle('" + listName + "')/items",
        type: "POST",
        contentType: "application/json;odata=verbose",
        data: JSON.stringify(item),
        headers: {
            "Accept": "application/json;odata=verbose",
            "X-RequestDigest": $("#__REQUESTDIGEST").val()
        },
        success: function (data) {
            success(data);
        },
        error: function (data) {
            failure(data);
        }
    });
}

// Get List Item Type metadata
function GetItemTypeForListName(name) {
    return "SP.Data." + name.charAt(0).toUpperCase() + name.split(" ").join("").slice(1) + "ListItem";
}

Found here: https://tjendarta.wordpress.com/2014/02/20/create-retrieve-update-and-delete-sharepoint-list-item-using-rest-api-and-jquery/

And referenced here: Adding new list item using REST