I have data that looks like this:

```
var data = [
    {item1: 123, item2: "name", item3: "id"},
    {item1: 234, item2: "other"},
    {item1: 456, item2: "another"},
    {item1: 789, item2: "again"}
]

```

How do I loop through and find if item3 is there, and if it isn't, fill it with something.