chore(abstract-mapreduce): replace var with const (#8880)

Replace `var` with `const` declarations.

Author: SourceR85

packages/node_modules/pouchdb-abstract-mapreduce/src/index.js

@@ -32,9 +32,9 @@ import {
   BuiltInError
 } from 'pouchdb-mapreduce-utils';
 
-var persistentQueues = {};
-var tempViewQueue = new TaskQueue();
-var CHANGES_BATCH_SIZE = 50;
+const persistentQueues = {};
+const tempViewQueue = new TaskQueue();
+const CHANGES_BATCH_SIZE = 50;
 
 function parseViewName(name) {
   // can be either 'ddocname/viewname' or just 'viewname'
@@ -612,12 +612,12 @@ function createAbstractMapReduce(localDocName, mapper, reducer, ddocValidator) {
     }
 
     function processBatch(response, purges) {
-      var results = response.results;
+      const results = response.results;
       if (!results.length && !purges.length) {
         return;
       }
 
-      for (let purge of purges) {
+      for (const purge of purges) {
         const index = results.findIndex(function (change) {
           return change.id === purge.docId;
         });
@@ -642,7 +642,7 @@ function createAbstractMapReduce(localDocName, mapper, reducer, ddocValidator) {
         }
       }
 
-      var docIdsToChangesAndEmits = createDocIdsToChangesAndEmits(results);
+      const docIdsToChangesAndEmits = createDocIdsToChangesAndEmits(results);
 
       queue.add(processChange(docIdsToChangesAndEmits, currentSeq));
 
@@ -840,13 +840,13 @@ function createAbstractMapReduce(localDocName, mapper, reducer, ddocValidator) {
           attachments: opts.attachments,
           binary: opts.binary
         });
-        var docIdsToDocs = new Map();
+        const docIdsToDocs = new Map();
         allDocsRes.rows.forEach(function (row) {
           docIdsToDocs.set(row.id, row.doc);
         });
         rows.forEach(function (row) {
-          var docId = rowToDocId(row);
-          var doc = docIdsToDocs.get(docId);
+          const docId = rowToDocId(row);
+          const doc = docIdsToDocs.get(docId);
           if (doc) {
             row.doc = doc;
           }