Catalog Client Script: Normalise and reset MRVS rows when a controlling variable changes - Pull 1 (#2360)

* Add README for MRVS normalisation client script

This README explains how to normalise and reset MRVS rows based on changes to a controlling variable, detailing setup and usage.

* Add MRVS normalization and reset on change

* Add function to reset specific MRVS columns

Author: hanna-g-sn

Client-Side Components/Catalog Client Script/Normalise and Reset a MRVS based on Variable Changes/README.md

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+# MRVS - Normalise and Reset Rows on Change
+
+## What this solves
+When a controlling variable changes (for example, Environment), existing MRVS rows may no longer be valid. This client script:
+- Clears or normalises specific MRVS columns
+- Deduplicates rows
+- Optionally sorts rows for a cleaner UX
+- Works entirely client-side using MRVS JSON
+
+## Where to use
+Catalog Item → OnChange client script on your controlling variable.
+
+## How it works
+- Reads the MRVS value as JSON via `g_form.getValue('my_mrvs')`
+- Applies transforms (clear columns, unique by key, sort)
+- Writes back the JSON with `g_form.setValue('my_mrvs', JSON.stringify(rows))`
+
+## Setup
+1. Replace `CONTROLLING_VARIABLE` with your variable name.
+2. Replace `MY_MRVS` with your MRVS variable name.
+3. Adjust `COLUMNS_TO_CLEAR`, `UNIQUE_KEY`, and `SORT_BY` as needed.
+
+## Notes
+- To clear the MRVS entirely, set `rows = []` before `setValue`.
+- Works with Catalog Client Scripts; no server call required.
+
+## References
+- GlideForm API (client): `getValue`, `setValue`, `clearValue`  
+  https://www.servicenow.com/docs/bundle/zurich-api-reference/page/app-store/dev_portal/API_reference/GlideForm/concept/c_GlideFormAPI.html
+- Working with MRVS values on the client (community examples)  
+  https://www.servicenow.com/community/developer-articles/accessing-multi-row-variable-set-value-outside-the-multi-row/ta-p/2308876

Client-Side Components/Catalog Client Script/Normalise and Reset a MRVS based on Variable Changes/mrvs_normalise_onchange.js

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+function onChange(control, oldValue, newValue, isLoading) {
+  if (isLoading) return;
+
+  var MRVS_NAME = 'MY_MRVS';                 // your MRVS variable name
+  var COLUMNS_TO_CLEAR = ['env', 'owner'];   // MRVS column names to clear
+  var UNIQUE_KEY = 'hostname';               // MRVS column that should be unique
+  var SORT_BY = 'hostname';                  // MRVS column to sort by
+
+  try {
+    var raw = g_form.getValue(MRVS_NAME);
+    var rows = raw ? JSON.parse(raw) : [];
+    if (!Array.isArray(rows)) rows = [];
+
+    // Clear specified columns
+    rows.forEach(function(row) {
+      COLUMNS_TO_CLEAR.forEach(function(col) { if (row.hasOwnProperty(col)) row[col] = ''; });
+    });
+
+    // Deduplicate by UNIQUE_KEY
+    if (UNIQUE_KEY) {
+      var seen = {};
+      rows = rows.filter(function(row) {
+        var key = String(row[UNIQUE_KEY] || '').toLowerCase();
+        if (!key || seen[key]) return false;
+        seen[key] = true;
+        return true;
+      });
+    }
+
+    // Sort (case-insensitive)
+    if (SORT_BY) {
+      rows.sort(function(a, b) {
+        var A = String(a[SORT_BY] || '').toLowerCase();
+        var B = String(b[SORT_BY] || '').toLowerCase();
+        if (A < B) return -1;
+        if (A > B) return 1;
+        return 0;
+      });
+    }
+
+    g_form.setValue(MRVS_NAME, JSON.stringify(rows));
+  } catch (e) {
+    console.error('MRVS normalise failed', e);
+  }
+}

Client-Side Components/Catalog Client Script/Normalise and Reset a MRVS based on Variable Changes/variant_reset_specific_columns.js

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+function onChange(control, oldValue, newValue, isLoading) {
+  if (isLoading) return;
+
+  var MRVS_NAME = 'MY_MRVS';
+  var COLUMNS_TO_CLEAR = ['env', 'region'];
+
+  var rows = [];
+  try { rows = JSON.parse(g_form.getValue(MRVS_NAME) || '[]'); } catch (e) {}
+  if (!Array.isArray(rows)) rows = [];
+
+  rows.forEach(function(row) {
+    COLUMNS_TO_CLEAR.forEach(function(col) { if (row.hasOwnProperty(col)) row[col] = ''; });
+  });
+
+  g_form.setValue(MRVS_NAME, JSON.stringify(rows));
+}
+