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# lodash.upperfirst
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lodash.upperfirst provides the `upperFirst` utility function that converts the first character of a string to uppercase while preserving the rest unchanged. It includes sophisticated Unicode handling with support for astral plane characters, combining marks, and zero-width joiners, making it ideal for internationalization and proper text formatting.
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## Package Information
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- **Package Name**: lodash.upperfirst
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- **Package Type**: npm
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- **Language**: JavaScript
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- **Installation**: `npm install lodash.upperfirst`
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## Core Imports
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```javascript
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var upperFirst = require('lodash.upperfirst');
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```
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## Basic Usage
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```javascript
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var upperFirst = require('lodash.upperfirst');
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// Basic string capitalization
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upperFirst('fred');
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// => 'Fred'
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// Already uppercase
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upperFirst('FRED');
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// => 'FRED'
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// Empty string
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upperFirst('');
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// => ''
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// Unicode characters
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upperFirst('émilie');
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// => 'Émilie'
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// Works with null/undefined
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upperFirst(null);
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// => ''
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upperFirst(undefined);
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// => ''
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```
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## Capabilities
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### String Case Conversion
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Converts the first character of string to upper case with full Unicode support.
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```javascript { .api }
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/**
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 * Converts the first character of `string` to upper case.
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 * 
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 * @param {string} [string=''] The string to convert.
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 * @returns {string} Returns the converted string.
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 */
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function upperFirst(string)
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```
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**Parameters:**
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- `string` (string, optional): The string to convert. Defaults to empty string if not provided.
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**Returns:**
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- (string): Returns the converted string with first character in uppercase
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**Key Features:**
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- **Unicode-aware**: Properly handles complex Unicode sequences including emojis, accented characters, and combining marks
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- **Astral plane support**: Correctly processes characters from the astral planes (U+10000 to U+10FFFF)
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- **Zero-width joiner handling**: Preserves zero-width joiners and variation selectors in complex scripts
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- **Null-safe**: Gracefully handles null, undefined, and non-string inputs by converting them to empty strings first
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- **Performance optimized**: Uses efficient regex patterns and optimized string processing for both ASCII and Unicode text
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**Unicode Examples:**
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```javascript
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// Emoji with skin tone modifiers - emoji stays unchanged (no uppercase form)
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upperFirst('👨🏽‍💻developer');
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// => '👨🏽‍💻developer' (emoji treated as single character, has no uppercase)
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// Complex Unicode sequences
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upperFirst('नमस्ते world');
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// => 'नमस्ते world'
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// Arabic with combining marks
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upperFirst('أهلاً');
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// => 'أهلاً'
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// Accented characters
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upperFirst('naïve');
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// => 'Naïve'
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```
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**Type Conversion Examples:**
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```javascript
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// Numbers are converted to strings first
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upperFirst(123);
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// => '123'
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// Booleans are converted to strings first
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upperFirst(true);
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// => 'True'
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// Arrays are converted to strings first
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upperFirst([1, 2, 3]);
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// => '1,2,3'
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```