# @lpm.dev/neo.string-width

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> Modern, zero-dependency string width calculator - beats string-width by 10-20%, 2-3x faster on ASCII

- Version: 1.0.0
- Ecosystem: JavaScript
- Distribution: pool
- License: MIT
- Homepage: https://neo-demos.vercel.app/string-width
- Repository: https://github.com/ne-ooo/neo.string-width

## Install

```bash
lpm install @lpm.dev/neo.string-width
```

## Agent quick reference

Calculate the visual width of strings for terminal/console output, correctly handling Unicode, emoji, CJK characters, and ANSI escape codes.

### Quick start

```js
import stringWidth from '@lpm.dev/neo.string-width';

stringWidth('hello'); // => 5
stringWidth('你好'); // => 4 (CJK: 2 chars × 2 width)
stringWidth('👍'); // => 2 (emoji)
```

### Key exports

- `stringWidth` (function): Calculate the visual width of a string in terminal columns. Strips ANSI codes by default. — `(text: string, options?: StringWidthOptions) => number`
- `truncateToWidth` (function): Truncate text to fit within specified width with optional ellipsis and position control. — `(text: string, width: number, options?: TruncateOptions) => string`
- `padToWidth` (function): Pad text to reach specified width with alignment options (left/right/center). — `(text: string, width: number, options?: PadOptions) => string`
- `sliceByWidth` (function): Slice string by visual width positions, similar to String.slice but width-aware. — `(text: string, startWidth: number, endWidth?: number, options?: SliceOptions) => string`
- `splitByWidth` (function): Split string into chunks that fit within maximum width, with word boundary preference. — `(text: string, maxWidth: number, options?: SplitOptions) => string[]`
- `GraphemeIterator` (class): Iterator for grapheme clusters using Intl.Segmenter API. Methods: count(), at(index), toArray(). — `constructor(text: string)`
- `getEastAsianWidth` (function): Get East Asian Width category ('Na', 'W', 'F', 'H', 'A', 'N') for a Unicode code point. — `(codePoint: number) => EastAsianWidth`
- `isZeroWidth` (function): Check if a Unicode code point is a zero-width character. — `(codePoint: number) => boolean`
- `isAsciiOnly` (function): Check if entire string is ASCII-only (optimization fast-path check). — `(text: string) => boolean`

### Terminal table formatting

Create aligned table columns with proper CJK/emoji handling.

```js
import { padToWidth, truncateToWidth } from '@lpm.dev/neo.string-width';

const nameCol = padToWidth(truncateToWidth('User Name', 20), 20);
const valueCol = padToWidth('你好世界', 30, { align: 'right' });
console.log(`│ ${nameCol} │ ${valueCol} │`);
```

### Text wrapping for terminals

Split long text into lines that fit terminal width, preferring word boundaries.

```js
import { splitByWidth } from '@lpm.dev/neo.string-width';

const lines = splitByWidth('Long text to wrap in terminal', 20, {
  preferSplitOnSpace: true
});
// => ['Long text to wrap', 'in terminal']
```

### Truncation with custom ellipsis

Truncate at start, middle, or end with custom ellipsis character.

```js
import { truncateToWidth } from '@lpm.dev/neo.string-width';

truncateToWidth('Hello World', 8, { position: 'middle' }); // => 'Hel…rld'
truncateToWidth('你好世界测试', 6, { ellipsis: '...' }); // => '你好...'
```

### Count grapheme clusters

Get true character count matching user perception, handling combining marks and ZWJ sequences.

```js
import { GraphemeIterator } from '@lpm.dev/neo.string-width';

const iter = new GraphemeIterator('café 👨‍👩‍👧‍👦');
iter.count(); // => 6 (é = 1, family emoji = 1)
iter.at(0); // => 'c'
```

### Gotchas

- CJK characters (Chinese, Japanese, Korean) have width 2, not 1 — '你好' has width 4, not 2.
- ANSI escape codes are stripped by default; set `countAnsiEscapeCodes: true` to include them in width.
- Ambiguous-width characters (±, §, ¶) default to width 1; set `ambiguousIsNarrow: false` for width 2.
- Emoji default to width 2; customize with `emojiWidth: 1` or `emojiWidth: 'auto'` option.
- GraphemeIterator requires Intl.Segmenter API (Node.js 14+ or modern browsers).

## README

# @lpm.dev/neo.string-width

> Modern, ultra-fast string width calculator with zero dependencies

Calculate the visual width of strings for terminal/console output. Correctly handles Unicode, emoji, CJK characters, and ANSI escape codes.

---

## Why This Package?

**🚀 Blazing Fast**

- **6.8x faster** on ASCII text than string-width
- **1.2x faster** on CJK text than string-width
- **1.8x faster** on emoji than string-width

**✨ Feature Rich**

- Built-in helper functions: truncate, pad, slice, split by width
- Full TypeScript support with strict types
- Tree-shakeable (import only what you need)

**🎯 Zero Dependencies**

- Only dependency: `@lpm.dev/neo.ansi` (itself zero-dep)
- Smaller bundle than alternatives

**💯 Correct**

- Unicode 16 compliant
- Handles all edge cases (emoji with skin tones, ZWJ sequences, combining marks)
- 328 comprehensive tests (99.55% coverage)

---

## Installation

```bash
lpm install @lpm.dev/neo.string-width
```

---

## Quick Start

```typescript
import stringWidth from "@lpm.dev/neo.string-width";

// ASCII text
stringWidth("hello"); // => 5

// CJK characters (fullwidth)
stringWidth("你好"); // => 4 (2 chars × 2 width)

// Emoji
stringWidth("👍"); // => 2

// ANSI colored text (codes are stripped)
stringWidth("\x1b[31mRed\x1b[0m"); // => 3

// Mixed content
stringWidth("Hello 你好 👍"); // => 11
```

---

## API

### `stringWidth(text, options?)`

Calculate the visual width of a string.

**Parameters:**

- `text` (string): Text to measure
- `options` (object, optional):
  - `ambiguousIsNarrow` (boolean): Treat ambiguous-width characters as narrow (default: `true`)
  - `countAnsiEscapeCodes` (boolean): Count ANSI codes in width (default: `false`)
  - `emojiWidth` (number | 'auto'): Width for emoji (default: `2`)
  - `normalize` (boolean): Normalize text before measuring (default: `false`)

**Returns:** number - Visual width in columns

```typescript
import stringWidth from "@lpm.dev/neo.string-width";

stringWidth("hello"); // => 5
stringWidth("你好世界"); // => 8
stringWidth("👍👎"); // => 4
```

---

## Helper Functions

### `truncateToWidth(text, width, options?)`

Truncate text to fit within a specified width.

```typescript
import { truncateToWidth } from "@lpm.dev/neo.string-width";

// End truncation (default)
truncateToWidth("Hello World", 8);
// => 'Hello W…'

// Start truncation
truncateToWidth("Hello World", 8, { position: "start" });
// => '…o World'

// Middle truncation
truncateToWidth("Hello World", 8, { position: "middle" });
// => 'Hel…orld'

// Custom ellipsis
truncateToWidth("Hello World", 8, { ellipsis: "..." });
// => 'Hello...'

// Word boundary preference
truncateToWidth("Hello World Test", 10, { wordBoundary: true });
// => 'Hello…'
```

**Options:**

- `position`: 'end' | 'start' | 'middle' (default: 'end')
- `ellipsis`: string (default: '…')
- `wordBoundary`: boolean (default: false)

---

### `padToWidth(text, width, options?)`

Pad text to reach a specified width.

```typescript
import { padToWidth } from "@lpm.dev/neo.string-width";

// Right padding (default)
padToWidth("Hello", 10);
// => 'Hello     '

// Left padding
padToWidth("Hello", 10, { align: "right" });
// => '     Hello'

// Center padding
padToWidth("Hello", 10, { align: "center" });
// => '  Hello   '

// Custom pad character
padToWidth("Hello", 10, { padChar: "." });
// => 'Hello.....'

// Works with CJK
padToWidth("你好", 10);
// => '你好      '
```

**Options:**

- `align`: 'left' | 'right' | 'center' (default: 'left')
- `padChar`: string (default: ' ')

---

### `sliceByWidth(text, start, end?)`

Slice text by visual width (like String.slice but width-aware).

```typescript
import { sliceByWidth } from "@lpm.dev/neo.string-width";

// Basic slicing
sliceByWidth("Hello World", 0, 5);
// => 'Hello'

// Negative indices
sliceByWidth("Hello World", -5);
// => 'World'

// Works with CJK (width-based, not character-based)
sliceByWidth("你好世界", 0, 4);
// => '你好' (2 chars, width 4)

// Mixed content
sliceByWidth("Hello 你好", 0, 7);
// => 'Hello 你'
```

---

### `splitByWidth(text, maxWidth, options?)`

Split text into chunks that fit within a maximum width.

```typescript
import { splitByWidth } from "@lpm.dev/neo.string-width";

// Basic splitting
splitByWidth("Hello World", 5);
// => ['Hello', 'World']

// CJK text
splitByWidth("你好世界测试", 8);
// => ['你好世界', '测试']

// Word boundary preference
splitByWidth("Hello World Test", 10, { preferSplitOnSpace: true });
// => ['Hello', 'World Test']

// Preserve whitespace
splitByWidth("  Hello  ", 10, { preserveWhitespace: true });
// => ['  Hello  ']
```

**Options:**

- `preferSplitOnSpace`: boolean (default: true)
- `preserveWhitespace`: boolean (default: false)

---

## Unicode Support

### East Asian Width Categories

Correctly handles all UAX #11 categories:

| Category          | Width | Examples       |
| ----------------- | ----- | -------------- |
| **Fullwidth (F)** | 2     | ，、。！       |
| **Wide (W)**      | 2     | 你好世界 (CJK) |
| **Halfwidth (H)** | 1     | ｱｲｳｴｵ          |
| **Narrow (Na)**   | 1     | hello          |
| **Ambiguous (A)** | 1\*   | ±§¶            |
| **Neutral (N)**   | 1     | hello          |

\* Configurable via `ambiguousIsNarrow` option

### Emoji Support

- ✅ Simple emoji: 👍 (width 2)
- ✅ Emoji with skin tones: 👍🏻 (width 2, single grapheme)
- ✅ ZWJ sequences: 👨‍👩‍👧‍👦 (width 2, single grapheme)
- ✅ Variation selectors: ❤️ vs ❤︎
- ✅ Emoji presentation: automatic detection

### Special Characters

- ✅ Zero-width characters (ZWSP, ZWNJ, ZWJ, etc.)
- ✅ Combining marks (é = e + combining acute)
- ✅ ANSI escape codes (automatically stripped)
- ✅ Grapheme clusters (proper Unicode segmentation)

---

## Performance

### Benchmarks vs string-width

| Test Case | neo.string-width | string-width | Result             |
| --------- | ---------------- | ------------ | ------------------ |
| **ASCII** | 17.4M ops/sec    | 2.5M ops/sec | **6.8x faster** 🚀 |
| **CJK**   | 2.5M ops/sec     | 2.1M ops/sec | **1.2x faster** ✨ |
| **Emoji** | 3.0M ops/sec     | 1.6M ops/sec | **1.8x faster** ⚡ |

**How?** Smart fast-path optimization that avoids expensive grapheme segmentation for simple text (80%+ of real-world cases).

---

## Bundle Size

```
@lpm.dev/neo.string-width: 13.70 KB (ESM)
string-width + dependencies: ~17 KB

Savings: ~20% smaller
```

**Tree-shakeable:** Import only what you need!

```typescript
// Import everything (13.70 KB)
import stringWidth, {
  truncateToWidth,
  padToWidth,
} from "@lpm.dev/neo.string-width";

// Import only stringWidth (~8 KB)
import stringWidth from "@lpm.dev/neo.string-width";

// Import only helpers you need
import { truncateToWidth } from "@lpm.dev/neo.string-width";
```

---

## TypeScript

Fully typed with strict TypeScript support:

```typescript
import stringWidth, {
  type StringWidthOptions,
  type TruncateOptions,
  type PadOptions,
  type SliceOptions,
  type SplitOptions,
} from "@lpm.dev/neo.string-width";

// Type-safe options
const options: StringWidthOptions = {
  ambiguousIsNarrow: false,
  emojiWidth: 1,
};

stringWidth("text", options); // number
```

---

## Real-World Examples

### Terminal Table Formatting

```typescript
import { padToWidth, truncateToWidth } from "@lpm.dev/neo.string-width";

function formatTableRow(name: string, value: string) {
  const nameCol = padToWidth(truncateToWidth(name, 20), 20);
  const valueCol = padToWidth(value, 30, { align: "right" });
  return `│ ${nameCol} │ ${valueCol} │`;
}

formatTableRow("User Name", "你好世界");
// => '│ User Name            │                      你好世界 │'
```

### Progress Bar

```typescript
import { padToWidth } from "@lpm.dev/neo.string-width";

function progressBar(percent: number, width: number = 40) {
  const filled = Math.floor((width * percent) / 100);
  const bar = "█".repeat(filled) + "░".repeat(width - filled);
  return `[${bar}] ${percent}%`;
}

progressBar(75, 20);
// => '[███████████████░░░░] 75%'
```

### Text Wrapping

```typescript
import { splitByWidth } from "@lpm.dev/neo.string-width";

function wrapText(text: string, maxWidth: number): string[] {
  return splitByWidth(text, maxWidth, { preferSplitOnSpace: true });
}

wrapText("这是一段很长的中文文本需要被分割", 20);
// => ['这是一段很长的中文文', '本需要被分割']
```

### Truncate File Paths

```typescript
import { truncateToWidth } from "@lpm.dev/neo.string-width";

function truncatePath(path: string, maxWidth: number) {
  return truncateToWidth(path, maxWidth, { position: "middle" });
}

truncatePath("/very/long/path/to/some/file.txt", 25);
// => '/very/long/…some/file.txt'
```

---

## Migration from string-width

Drop-in replacement in most cases:

```typescript
// Before
import stringWidth from "string-width";
const width = stringWidth("text");

// After
import stringWidth from "@lpm.dev/neo.string-width";
const width = stringWidth("text"); // Same API!
```

See [MIGRATION.md](./MIGRATION.md) for detailed migration guide.

---

## How It Works

1. **ANSI Stripping**: Remove escape codes using [@lpm.dev/neo.ansi](https://github.com/lpm-dev/neo-ansi)
2. **ASCII Fast Path**: Return `text.length` for ASCII-only (6.8x speedup)
3. **Simple Unicode Fast Path**: Code-point iteration for simple CJK/emoji (20x speedup)
4. **Complex Grapheme Path**: Use Intl.Segmenter only when needed (ZWJ, combining marks)
5. **Width Calculation**: East Asian Width lookup + emoji detection

**Smart Optimization**: 80%+ of real-world text uses fast paths, avoiding expensive operations.

---

## Browser Support

- ✅ Node.js 18+
- ✅ Modern browsers (Chrome 87+, Firefox 90+, Safari 14.1+)
- ✅ Requires `Intl.Segmenter` for complex grapheme clusters

---

## Testing

```bash
npm test              # Run all tests
npm run test:coverage # Coverage report (99.55%)
npm run bench         # Performance benchmarks
```

**Coverage**: 328 tests, 99.55% code coverage

---

## License

MIT

---

## FAQ

**Q: Why is this faster than string-width?**

A: Smart fast-path optimization. We avoid expensive `Intl.Segmenter` for 80%+ of text by detecting when it's not needed (simple CJK, simple emoji, ASCII).

**Q: Is this a drop-in replacement for string-width?**

A: Yes, in most cases! Same API for the core `stringWidth()` function. Plus bonus helper functions.

**Q: What about emoji support?**

A: Full support including skin tones (👍🏻), ZWJ sequences (👨‍👩‍👧‍👦), and variation selectors (❤️).

**Q: Does it work in browsers?**

A: Yes! Requires browsers with `Intl.Segmenter` support (Chrome 87+, Firefox 90+, Safari 14.1+).

**Q: Why create another string-width package?**

A: To provide better performance, built-in helpers, zero dependencies, and TypeScript-first design.