I'm trying to add an item to a SharePoint list like so:

Title  |  Column1  |  Column2
-------+-----------+-----------
title1 |        1  |  a
title2 |        2  |  b

Now lets say I want to add

title3 |        3  | c

Using the following function:

var listColumnNames = ["Column1", "Column2"];

function addNewItem(title, columns) {

    var itemCreateInfo = new SP.ListItemCreationInformation();
    var newListItem = list.addItem(itemCreateInfo);

    // this works, it will create a new row with the title
    newListItem.set_item("Title", title); 

    // this throws the error below  
    newListItem.set_item("Column1", "test"); 

    // this does nothing
    newListItem["Column1"] = "test"; 

    // this is my ultimate goal, but also doesn't work
    for (var i = 0 ; i < listColumnNames.length ; i++)
        newListItem.set_item(listColumnNames[i], columns[i])

    newListItem.update();
    context.load(newListItem);
    context.executeQueryAsync(querySuccess, queryFailed);
}

But I get this error:

Column 'Column1' does not exist. It may have been deleted by another user. /MyPath/MyListName undefined

In this tutorial: http://adicodes.com/add-update-and-delete-list-items-using-ecmascript/

It omits the lines I need, but it seems like what I'm doing is the right idea:

newItem.set_item('Title', 'This is new item');

// set values to other columns of the list here

newItem.update();

In the docs: https://msdn.microsoft.com/en-us/library/office/hh185011(v=office.14).aspx

It shows doing something that looks like what I'm doing, but it doesn't clarify whether "Body" is actually the column name or some other attribute I'm unaware of.

oListItem.set_item('Title', 'My New Item!');

oListItem.set_item('Body', 'Hello World!');
    
oListItem.update();

Can anyone see what I'm doing wrong?

Thank you in advance, and sorry for asking so many questions. I just started this and am trying to get my bearings.

I'm trying to add an item to a SharePoint list like so:

Title  |  Column1  |  Column2
-------+-----------+-----------
title1 |        1  |  a
title2 |        2  |  b

Now lets say I want to add

title3 |        3  | c

Using the following function:

var listColumnNames = ["Column1", "Column2"];

function addNewItem(title, columns) {

    var itemCreateInfo = new SP.ListItemCreationInformation();
    var newListItem = list.addItem(itemCreateInfo);

    // this works, it will create a new row with the title
    newListItem.set_item("Title", title); 

    // this throws the error below  
    newListItem.set_item("Column1", "test"); 

    // this does nothing
    newListItem["Column1"] = "test"; 

    // this is my ultimate goal, but also doesn't work
    for (var i = 0 ; i < listColumnNames.length ; i++)
        newListItem.set_item(listColumnNames[i], columns[i])

    newListItem.update();
    context.load(newListItem);
    context.executeQueryAsync(querySuccess, queryFailed);
}

But I get this error:

Column 'Column1' does not exist. It may have been deleted by another user. /MyPath/MyListName undefined

In this tutorial: http://adicodes.com/add-update-and-delete-list-items-using-ecmascript/

It omits the lines I need, but it seems like what I'm doing is the right idea:

newItem.set_item('Title', 'This is new item');

// set values to other columns of the list here

newItem.update();

In the docs: https://msdn.microsoft.com/en-us/library/office/hh185011(v=office.14).aspx

It shows doing something that looks like what I'm doing, but it doesn't clarify whether "Body" is actually the column name or some other attribute I'm unaware of.

oListItem.set_item('Title', 'My New Item!');

oListItem.set_item('Body', 'Hello World!');
    
oListItem.update();

Can anyone see what I'm doing wrong?