adds passAdjacentKeyFields option (#682)

Author: MikeWillis

README.md

@@ -168,6 +168,7 @@ When the breakpoint is reached the column will be hidden. These are the built-in
 | noTableHead | bool | no | false | hides the the sort columns and titles (TableHead) - this will obviously negate sorting |
 | persistTableHead | bool | no |  | Show the table head (columns) even when `progressPending` is true. Note that the `noTableHead` will always hide the table head (columns) even when using  `persistTableHead` |
 | direction | string | no | auto | Accepts: `ltr, rtl, or auto`. When set to `auto` (default), RDT will attempt to detect direction by checking the HTML and DIV tags. For cases where you need to force rtl, or ltr just set this option manually (i.e. SSR) |
+| passAdjacentKeyFields | bool | no | false | Adds `prevKeyField` and `nextKeyField` properties to the row object, containing the keyField value for the adjacent rows, if any |
 
 #### Row Selection
 

src/DataTable/DataTable.js

@@ -103,6 +103,7 @@ const DataTable = memo(({
   theme,
   customStyles,
   direction,
+  passAdjacentKeyFields,
 }) => {
   const initialState = {
     allSelected: false,
@@ -388,6 +389,12 @@ const DataTable = memo(({
                       && expandableRowDisabled
                       && expandableRowDisabled(row);
 
+
+                    if ( passAdjacentKeyFields ) {
+                       row.prevKeyField = typeof(calculatedRows[i-1]) != "undefined" ? calculatedRows[i-1][keyField] : false;
+                       row.nextKeyField = typeof(calculatedRows[i+1]) != "undefined" ? calculatedRows[i+1][keyField] : false;
+                    }
+
                     return (
                       <TableRow
                         id={id}