ReactJS Program to Sorting With useMemo with Explanation
ReactJS
Medium
Performance & Patterns
33 views
1 min read
90 words
This problem helps you practice core ReactJS fundamentals in a practical way. It builds intuition around sorting, usememo, sort. Let’s break it down step by step so you can implement it confidently.
Problem Statement
Sort a list only when sort options change, not on every render.
Input Format
No input.
Output Format
Render a React component.
Constraints
Use useMemo for sorting and avoid mutating the original array.
Code Solution
This explanation is written for learning purposes and to help beginners understand the concept clearly.
import React, { useMemo, useState } from 'react';
const base = [
{ id: 1, title: 'meetcode arrays' },
{ id: 2, title: 'meetcode hooks' },
{ id: 3, title: 'meetcode forms' },
{ id: 4, title: 'meetcode state' }
];
export default function App() {
const [dir, setDir] = useState('asc');
const [ticks, setTicks] = useState(0);
const sorted = useMemo(() => {
const copy = [...base];
copy.sort((a, b) => a.title.localeCompare(b.title));
if (dir === 'desc') copy.reverse();
return copy;
}, [dir]);
return (
<div style={{ padding: 16, width: 520 }}>
<h2 style={{ marginTop: 0 }}>Sort list</h2>
<div style={{ display: 'flex', gap: 10 }}>
<button type='button' onClick={() => setDir((d) => (d === 'asc' ? 'desc' : 'asc'))} style={{ padding: '10px 14px', borderRadius: 12, border: 0, background: '#0b5', color: '#fff' }}>Direction: {dir}</button>
<button type='button' onClick={() => setTicks((t) => t + 1)} style={{ padding: '10px 14px', borderRadius: 12, border: '1px solid #ddd', background: '#fff' }}>Unrelated: {ticks}</button>
</div>
<ul style={{ marginTop: 12 }}>
{sorted.map((x) => <li key={x.id}>{x.title}</li>)}
</ul>
</div>
);
}
Output Example
No sample I/O is provided for this question.
Common Mistakes
- Misreading input/output format.
- Not handling constraints and edge cases.
- Off-by-one errors in loops.
- Forgetting to reset variables between test cases (if any).
Solution Guide
Problem
Sort a list only when sort options change, not on every render.
Input / Output
Output
Render a React component.
Constraints
Use useMemo for sorting and avoid mutating the original array.
Details
Common Mistakes
- Misreading input/output format.
- Not handling constraints and edge cases.
- Off-by-one errors in loops.
- Forgetting to reset variables between test cases (if any).
Difficulty
Medium
ReactJS
Official Solution
import React, { useMemo, useState } from 'react';
const base = [
{ id: 1, title: 'meetcode arrays' },
{ id: 2, title: 'meetcode hooks' },
{ id: 3, title: 'meetcode forms' },
{ id: 4, title: 'meetcode state' }
];
export default function App() {
const [dir, setDir] = useState('asc');
const [ticks, setTicks] = useState(0);
const sorted = useMemo(() => {
const copy = [...base];
copy.sort((a, b) => a.title.localeCompare(b.title));
if (dir === 'desc') copy.reverse();
return copy;
}, [dir]);
return (
<div style={{ padding: 16, width: 520 }}>
<h2 style={{ marginTop: 0 }}>Sort list</h2>
<div style={{ display: 'flex', gap: 10 }}>
<button type='button' onClick={() => setDir((d) => (d === 'asc' ? 'desc' : 'asc'))} style={{ padding: '10px 14px', borderRadius: 12, border: 0, background: '#0b5', color: '#fff' }}>Direction: {dir}</button>
<button type='button' onClick={() => setTicks((t) => t + 1)} style={{ padding: '10px 14px', borderRadius: 12, border: '1px solid #ddd', background: '#fff' }}>Unrelated: {ticks}</button>
</div>
<ul style={{ marginTop: 12 }}>
{sorted.map((x) => <li key={x.id}>{x.title}</li>)}
</ul>
</div>
);
}
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