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# is-fullwidth-code-point
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Check if the character represented by a given Unicode code point is fullwidth. This package determines whether a Unicode code point represents a character that occupies two columns in monospace environments, which is essential for proper text layout in terminals, text editors, and CLI applications.
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## Package Information
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- **Package Name**: is-fullwidth-code-point
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- **Package Type**: npm  
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- **Language**: JavaScript (ES Module)
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- **Installation**: `npm install is-fullwidth-code-point`
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## Core Imports
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```javascript
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import isFullwidthCodePoint from 'is-fullwidth-code-point';
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```
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For environments that support dynamic imports:
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```javascript
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const { default: isFullwidthCodePoint } = await import('is-fullwidth-code-point');
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```
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## Architecture
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This package provides a simple utility function with a focused API surface:
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- **Single Function Export**: Default export of `isFullwidthCodePoint` function
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- **Input Validation**: Uses `Number.isInteger()` for robust parameter checking
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- **Unicode Classification**: Delegates to `get-east-asian-width` library for accurate East Asian Width property determination
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- **Error Handling**: Returns `false` for invalid inputs rather than throwing exceptions
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- **Zero Dependencies**: Apart from the classification library, no additional runtime dependencies
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## Basic Usage
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```javascript
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import isFullwidthCodePoint from 'is-fullwidth-code-point';
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// Check East Asian characters (fullwidth)
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isFullwidthCodePoint('谢'.codePointAt(0)); // => true
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isFullwidthCodePoint('あ'.codePointAt(0)); // => true  
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isFullwidthCodePoint('고'.codePointAt(0)); // => true
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// Check ASCII characters (halfwidth)
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isFullwidthCodePoint('a'.codePointAt(0)); // => false
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isFullwidthCodePoint('1'.codePointAt(0)); // => false
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// Using Unicode code points directly
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isFullwidthCodePoint(0x1F251); // => true (emoji)
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isFullwidthCodePoint(0x1B11E); // => true (musical symbol)
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isFullwidthCodePoint(0x201D);  // => false (punctuation)
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```
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## Capabilities
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### Fullwidth Code Point Detection
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Determines if a Unicode code point represents a fullwidth character according to Unicode East Asian Width properties. Returns true for characters classified as either "Fullwidth (F)" or "Wide (W)" in the Unicode standard.
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```javascript { .api }
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/**
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 * Check if the character represented by a given Unicode code point is fullwidth
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 * @param codePoint - The Unicode code point of a character
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 * @returns true if the code point represents a fullwidth character, false otherwise
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 */
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export default function isFullwidthCodePoint(codePoint: number): boolean;
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```
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**Parameters:**
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- `codePoint` (number): The Unicode code point of a character. Must be an integer value.
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**Returns:**
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- `boolean`: Returns `true` if the code point represents a fullwidth character, `false` otherwise.
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**Behavior:**
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- Returns `false` for non-integer inputs (including `NaN`, floating point numbers, and non-numeric values)
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- Uses `Number.isInteger()` for input validation before processing
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- Delegates to the `get-east-asian-width` library for Unicode width classification
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- Returns `true` if the code point is classified as either "Fullwidth" or "Wide" according to Unicode East Asian Width standards
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- Handles the full Unicode range including emoji, symbols, and extended character sets
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**Error Handling:**
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- Invalid inputs (non-integers) return `false` rather than throwing exceptions
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- No exceptions are thrown for any input value
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**Usage Examples:**
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```javascript
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// Common East Asian characters
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isFullwidthCodePoint('中'.codePointAt(0)); // => true (Chinese)
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isFullwidthCodePoint('に'.codePointAt(0)); // => true (Japanese Hiragana)
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isFullwidthCodePoint('한'.codePointAt(0)); // => true (Korean Hangul)
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// Emoji and symbols
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isFullwidthCodePoint('😀'.codePointAt(0)); // => true (emoji)
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isFullwidthCodePoint('♪'.codePointAt(0));  // => true (musical note)
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// ASCII and Latin characters  
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isFullwidthCodePoint('A'.codePointAt(0));  // => false
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isFullwidthCodePoint(' '.codePointAt(0));  // => false (space)
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isFullwidthCodePoint('!'.codePointAt(0));  // => false (punctuation)
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// Edge cases
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isFullwidthCodePoint(NaN);        // => false
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isFullwidthCodePoint(3.14);       // => false (not integer)
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isFullwidthCodePoint(-1);         // => false (negative)
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isFullwidthCodePoint(0);          // => false (null character)
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```
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## Types
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```typescript { .api }
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// TypeScript type definitions (when using TypeScript)
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export default function isFullwidthCodePoint(codePoint: number): boolean;
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```
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## Dependencies
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This package depends on `get-east-asian-width` (version ^1.3.1) for Unicode width classification logic. Specifically, it imports and uses two internal functions:
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- `_isFullWidth`: Determines if a code point represents a fullwidth character (East Asian Width property "F")
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- `_isWide`: Determines if a code point represents a wide character (East Asian Width property "W")
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The function returns `true` if either classification returns `true`, covering all characters that occupy two columns in terminal and monospace font environments.