From a4375cb53265fb2481a2b57271e58395bb85a5b2 Mon Sep 17 00:00:00 2001
From: Cheton Wu <cheton@gmail.com>
Date: Sun, 21 Nov 2021 08:59:32 +0800
Subject: [PATCH] feat: remove array items without consuming extra memory (#59)

* feat: add remove-array-items that can remove items from an array without generating memory garbage

* chore: replace arr.splice(start, deleteCount) with removeArrayItems(arr, start, deleteCount)
---
 src/infinite-tree.js       | 17 +++++++------
 src/remove-array-items.js  | 27 ++++++++++++++++++++
 test/remove-array-items.js | 51 ++++++++++++++++++++++++++++++++++++++
 3 files changed, 87 insertions(+), 8 deletions(-)
 create mode 100644 src/remove-array-items.js
 create mode 100644 test/remove-array-items.js

diff --git a/src/infinite-tree.js b/src/infinite-tree.js
index f7fead4..eefd015 100644
--- a/src/infinite-tree.js
+++ b/src/infinite-tree.js
@@ -8,9 +8,10 @@ import { flatten, Node } from 'flattree';
 import Clusterize from './clusterize';
 import ensureArray from './ensure-array';
 import extend from './extend';
-import { get } from './utilities';
 import LookupTable from './lookup-table';
+import removeArrayItems from './remove-array-items';
 import { defaultRowRenderer } from './renderer';
+import { get } from './utilities';
 import {
     preventDefault,
     addEventListener,
@@ -749,8 +750,8 @@ class InfiniteTree extends events.EventEmitter {
             }
 
             // Update nodes & rows
-            this.nodes.splice(nodeIndex + 1, total);
-            this.rows.splice(nodeIndex + 1, total);
+            removeArrayItems(this.nodes, nodeIndex + 1, total);
+            removeArrayItems(this.rows, nodeIndex + 1, total);
 
             // Toggle the collapsing state
             node.state.collapsing = false;
@@ -1361,8 +1362,8 @@ class InfiniteTree extends events.EventEmitter {
 
         if (parentNodeIndex >= 0) {
             // Update nodes & rows
-            this.nodes.splice(parentNodeIndex + 1, deleteCount);
-            this.rows.splice(parentNodeIndex + 1, deleteCount);
+            removeArrayItems(this.nodes, parentNodeIndex + 1, deleteCount);
+            removeArrayItems(this.rows, parentNodeIndex + 1, deleteCount);
 
             // Update the row corresponding to the parent node
             this.rows[parentNodeIndex] = this.options.rowRenderer(parentNode, this.options);
@@ -1441,15 +1442,15 @@ class InfiniteTree extends events.EventEmitter {
         }
 
         // Update parent node
-        parentNode.children.splice(parentNode.children.indexOf(node), 1);
+        removeArrayItems(parentNode.children, parentNode.children.indexOf(node), 1);
         if (parentNode !== this.state.rootNode) {
             parentNode.state.open = parentNode.state.open && (parentNode.children.length > 0);
         }
 
         if (nodeIndex >= 0) {
             // Update nodes & rows
-            this.nodes.splice(nodeIndex, deleteCount);
-            this.rows.splice(nodeIndex, deleteCount);
+            removeArrayItems(this.nodes, nodeIndex, deleteCount);
+            removeArrayItems(this.rows, nodeIndex, deleteCount);
         }
 
         // Update the row corresponding to the parent node
diff --git a/src/remove-array-items.js b/src/remove-array-items.js
new file mode 100644
index 0000000..f5ca393
--- /dev/null
+++ b/src/remove-array-items.js
@@ -0,0 +1,27 @@
+/**
+ * Remove a range of items from an array.
+ *
+ * @function removeItems
+ * @param {Array<*>} arr The target array.
+ * @param {number} startIndex The index to begin removing from (inclusive).
+ * @param {number} removeCount How many items to remove.
+ */
+const removeArrayItems = (arr, startIndex, removeCount) => {
+    const length = arr.length;
+
+    if (startIndex >= length || removeCount <= 0 || startIndex < 0) {
+        return;
+    }
+
+    removeCount = (startIndex + removeCount > length ? length - startIndex : removeCount);
+
+    const len = length - removeCount;
+
+    for (let i = startIndex; i < len; ++i) {
+        arr[i] = arr[i + removeCount];
+    }
+
+    arr.length = len;
+};
+
+export default removeArrayItems;
diff --git a/test/remove-array-items.js b/test/remove-array-items.js
new file mode 100644
index 0000000..db787dd
--- /dev/null
+++ b/test/remove-array-items.js
@@ -0,0 +1,51 @@
+import { test } from 'tap';
+import removeArrayItems from '../src/remove-array-items';
+
+test('should return if the start index is greater than or equal to the length of the array', (t) => {
+    const arr = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
+    removeArrayItems(arr, arr.length + 1, 5);
+    t.equals(arr.length, 10);
+    t.end();
+})
+
+test('should return if the remove count is 0', (t) => {
+    const arr = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
+    removeArrayItems(arr, 2, 0);
+    t.equals(arr.length, 10);
+    t.end();
+});
+
+test('should remove the number of elements specified from the array, starting from the start index', (t) => {
+    const arr = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
+    removeArrayItems(arr, 3, 4);
+    t.deepEquals(arr, [1, 2, 3, 8, 9, 10]);
+    t.end();
+});
+
+test('should remove other elements if delete count is larger than the number of elements after start index', (t) => {
+    const arr = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
+    removeArrayItems(arr, 7, 10);
+    t.deepEquals(arr, [1, 2, 3, 4, 5, 6, 7]);
+    t.end();
+});
+
+test('should remove no element if count is less than or equal to zero', function (t) {
+    const arr = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
+    removeArrayItems(arr, 7, -2);
+    t.deepEquals(arr, [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]);
+    t.end();
+});
+
+test('should remove no element if start is less than or equal to zero', (t) => {
+    const arr = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
+    removeArrayItems(arr, -7, 5);
+    t.deepEquals(arr, [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]);
+    t.end();
+});
+
+test("should remove the remaining elements start with 'start' if count is greater than arr.length", (t) => {
+    const arr = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
+    removeArrayItems(arr, 4, 100);
+    t.deepEquals(arr, [1, 2, 3, 4]);
+    t.end();
+});