refactor(FilterExample): convert to functional component (#523)

Converts the FilterExample component from a class-based component to a functional component using React hooks.

Co-authored-by: google-labs-jules[bot] <161369871+google-labs-jules[bot]@users.noreply.github.com>

Author: jakezatecky

examples/src/js/FilterExample.jsx

@@ -1,111 +1,81 @@
-import React, { Component } from 'react';
+import React, { useState, useCallback, useEffect } from 'react';
 import CheckboxTree from 'react-checkbox-tree';
 
 import { fileSystem as nodes } from './common.js';
 
-class FilterExample extends Component {
-    state = {
-        checked: [
-            '/app/Http/Controllers/WelcomeController.js',
-            '/app/Http/routes.js',
-            '/public/assets/style.css',
-            '/public/index.html',
-            '/.gitignore',
-        ],
-        expanded: [
-            '/app',
-        ],
-        filterText: '',
-        filteredNodes: nodes,
-    };
-
-    constructor(props) {
-        super(props);
-
-        this.onCheck = this.onCheck.bind(this);
-        this.onExpand = this.onExpand.bind(this);
-        this.onFilterChange = this.onFilterChange.bind(this);
-        this.filterTree = this.filterTree.bind(this);
-        this.filterNodes = this.filterNodes.bind(this);
-    }
-
-    onCheck(checked) {
-        this.setState({ checked });
-    }
-
-    onExpand(expanded) {
-        this.setState({ expanded });
-    }
+function FilterExample() {
+    const [checked, setChecked] = useState([
+        '/app/Http/Controllers/WelcomeController.js',
+        '/app/Http/routes.js',
+        '/public/assets/style.css',
+        '/public/index.html',
+        '/.gitignore',
+    ]);
+    const [expanded, setExpanded] = useState(['/app']);
+    const [filterText, setFilterText] = useState('');
+    const [filteredNodes, setFilteredNodes] = useState(nodes);
+
+    const onCheck = useCallback((checkedValues) => {
+        setChecked(checkedValues);
+    }, []);
+
+    const onExpand = useCallback((expandedValues) => {
+        setExpanded(expandedValues);
+    }, []);
+
+    const onFilterChange = useCallback((e) => {
+        setFilterText(e.target.value);
+    }, []);
+
+    useEffect(() => {
+        const nodeMatchesSearchString = ({ label }) => (
+            label.toLocaleLowerCase().indexOf(filterText.toLocaleLowerCase()) > -1
+        );
 
-    onFilterChange(e) {
-        this.setState({ filterText: e.target.value }, this.filterTree);
-    }
+        const filterNodes = (filtered, node) => {
+            if (nodeMatchesSearchString(node)) {
+                // Node's label matches the search string
+                filtered.push(node);
+            } else {
+                // Find if any children match the search string or have descendants who do
+                const filteredChildren = (node.children || []).reduce(filterNodes, []);
+
+                // If so, render these children
+                if (filteredChildren.length > 0) {
+                    filtered.push({ ...node, children: filteredChildren });
+                }
+            }
 
-    filterTree() {
-        const { filterText } = this.state;
+            return filtered;
+        };
 
         // Reset nodes back to unfiltered state
         if (!filterText) {
-            this.setState({ filteredNodes: nodes });
-
+            setFilteredNodes(nodes);
             return;
         }
 
-        this.setState({
-            filteredNodes: nodes.reduce(this.filterNodes, []),
-        });
-    }
-
-    filterNodes(filtered, node) {
-        if (this.nodeMatchesSearchString(node)) {
-            // Node's label matches the search string
-            filtered.push(node);
-        } else {
-            // Find if any children match the search string or have descendants who do
-            const filteredChildren = (node.children || []).reduce(this.filterNodes, []);
-
-            // If so, render these children
-            if (filteredChildren.length > 0) {
-                filtered.push({ ...node, children: filteredChildren });
-            }
-        }
-
-        return filtered;
-    }
-
-    nodeMatchesSearchString({ label }) {
-        const { filterText } = this.state;
-
-        return label.toLocaleLowerCase().indexOf(filterText.toLocaleLowerCase()) > -1;
-    }
-
-    render() {
-        const {
-            checked,
-            expanded,
-            filterText,
-            filteredNodes,
-        } = this.state;
-
-        return (
-            <div className="filter-container">
-                <input
-                    className="filter-text"
-                    placeholder="Search..."
-                    type="text"
-                    value={filterText}
-                    onChange={this.onFilterChange}
-                />
-                <CheckboxTree
-                    checked={checked}
-                    expanded={expanded}
-                    nodes={filteredNodes}
-                    onCheck={this.onCheck}
-                    onExpand={this.onExpand}
-                />
-            </div>
-        );
-    }
+        setFilteredNodes(nodes.reduce(filterNodes, []));
+    }, [filterText]);
+
+    return (
+        <div className="filter-container">
+            <input
+                className="filter-text"
+                placeholder="Search..."
+                type="text"
+                value={filterText}
+                onChange={onFilterChange}
+            />
+            <CheckboxTree
+                checked={checked}
+                expanded={expanded}
+                nodes={filteredNodes}
+                onCheck={onCheck}
+                onExpand={onExpand}
+            />
+        </div>
+    );
 }
 
 export default FilterExample;