# Check if a rectangle contains another one

Compare corners: a contains b when b’s corners sit inside or on a’s edges.

Canonical: https://1loc.dev/math/check-if-a-rectangle-contains-other-one/
Version: 1.0.0
Runtime: JavaScript · Node.js 22 / modern browsers
Verification: Local fixtures; no external services
Updated: 2026-10-28

## Implementation

```javascript
function contains({ a, b }) { return a.x1 <= b.x1 && a.y1 <= b.y1 && a.x2 >= b.x2 && a.y2 >= b.y2; }
```

## Input

```json
{
  "a": {
    "x1": 0,
    "y1": 0,
    "x2": 10,
    "y2": 10
  },
  "b": {
    "x1": 2,
    "y1": 2,
    "x2": 5,
    "y2": 5
  }
}
```

## Expected output

```json
true
```

## Edge case

Input:
```json
{
  "a": {
    "x1": 0,
    "y1": 0,
    "x2": 4,
    "y2": 4
  },
  "b": {
    "x1": 2,
    "y1": 2,
    "x2": 5,
    "y2": 5
  }
}
```
Output:
```json
false
```

## Limits

- (x1, y1) is the top-left and (x2, y2) the bottom-right corner; the lab requires x1 ≤ x2 and y1 ≤ y2.
- Shared edges count as contained.

The lab validates types and size before calling this function. Add equivalent validation at your own trust boundary.

## Source and license

Original: https://github.com/phuocng/1loc/blob/14b481cf60dff1620ab1bb99a43b1f68068cdd9b/contents/check-if-a-rectangle-contains-other-one.mdx
Author: Nguyen Huu Phuoc and original contributors
Contributors: See original repository history
Source commit: 14b481cf60dff1620ab1bb99a43b1f68068cdd9b
Copyright (c) 2020 phuoc-ng
License: MIT — https://1loc.dev/licenses/
Maintainer: Oveyon
Modifications: Original comparison kept; single-object input, corner-order validation and edge semantics. Original MDX retained as inert source evidence.