Add, update and query SharePoint list items from CSOM using javascript

Question

Using javascript and SharePoint's CSOM, can someone provide an example for the follow scenario:

Get field value from the selected items in a list (ListA).

Then for each item selected, take a fields value and use it to query a different list (ListB).

If the query returns 0 rows, create item in ListB and update selected item in ListA.

Else if the query returns 1 row, update selected item in ListA.

Answer 1

This will get you started.

MSDN - How to: Complete basic operations using JavaScript library code in SharePoint 2013

It gives examples of how to

• Query lists and get value
• Add/update and delete records
• and many others common operations

So, most of what you need to complete your scenario.