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# is-svg
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is-svg provides a lightweight utility function for detecting whether a given string contains valid SVG (Scalable Vector Graphics) content. It performs XML validation and specifically identifies SVG format through proper XML parsing with configurable validation options.
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## Package Information
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- **Package Name**: is-svg
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- **Package Type**: npm
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- **Language**: TypeScript
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- **Installation**: `npm install is-svg`
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## Core Imports
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```typescript
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import isSvg from 'is-svg';
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```
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This package requires Node.js 20+ and only provides ES module exports.
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## Basic Usage
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```typescript
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import isSvg from 'is-svg';
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// Basic SVG detection
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isSvg('<svg xmlns="http://www.w3.org/2000/svg"><path fill="#00CD9F"/></svg>');
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//=> true
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isSvg('<div>Not SVG</div>');
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//=> false
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// Performance mode with reduced validation
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isSvg('<svg xmlns="http://www.w3.org/2000/svg"><rect/></svg>', {validate: false});
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//=> true
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// Full validation mode (default)
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isSvg('<svg xmlns="http://www.w3.org/2000/svg"><rect/></svg>', {validate: true});
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//=> true
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```
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## Capabilities
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### SVG Detection
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Checks if a string contains valid SVG content using XML validation.
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```typescript { .api }
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/**
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 * Check if a string is SVG
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 * @param string - The input string to check for SVG content
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 * @param options - Configuration options
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 * @returns true if the string contains valid SVG, false otherwise
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 * @throws TypeError if first argument is not a string
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 */
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function isSvg(string: string, options?: Options): boolean;
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interface Options {
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  /**
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   * Whether to validate the SVG as proper XML.
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   * Turning this off can improve performance significantly.
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   * @default true
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   */
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  validate?: boolean;
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}
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```
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**Behavior:**
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- Throws `TypeError` if the first argument is not a string
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- Trims input string and returns `false` for empty strings
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- Uses XML validation to determine if content is valid SVG
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- Returns `true` if the string contains valid SVG, `false` otherwise
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**Performance Considerations:**
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- Setting `validate: false` improves performance significantly by using chunked processing
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- Setting `validate: true` (default) provides thorough XML validation for accuracy
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- Package handles large strings efficiently and avoids quadratic regex behavior
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**Usage Examples:**
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```typescript
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import isSvg from 'is-svg';
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// Valid SVG examples
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isSvg('<svg xmlns="http://www.w3.org/2000/svg"></svg>');
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//=> true
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isSvg('<svg><rect width="100" height="100"/></svg>');
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//=> true
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// Invalid examples
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isSvg('<div>Not an SVG</div>');
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//=> false
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isSvg('');
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//=> false
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isSvg('   ');
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//=> false
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// Error handling
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try {
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  isSvg(123); // TypeError: Expected a `string`, got `number`
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} catch (error) {
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  console.error(error.message);
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}
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// Performance optimization for large files
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const largeSvgString = '...'; // Large SVG content
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const isValidSvg = isSvg(largeSvgString, {validate: false}); // Faster processing
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```
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## Error Handling
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The function throws a `TypeError` when the first argument is not a string:
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```typescript
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// This will throw: TypeError: Expected a `string`, got `number`
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isSvg(123);
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// This will throw: TypeError: Expected a `string`, got `undefined`
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isSvg();
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```
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For all other cases (invalid XML, non-SVG content, empty strings), the function returns `false` rather than throwing errors.