Tagged template literals allow custom processing of template strings. Here's how to use them for powerful string transformations.
Basic Syntax
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Raw Strings
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HTML Escaping
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SQL Query Builder
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CSS-in-JS
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Internationalization
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Logging with Context
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Highlight/Formatting
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GraphQL Queries
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Markdown Processing
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Regex Builder
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Dedent/Trim
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Caching Tag
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Type Coercion
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Best Practices
Use Cases:
✓ HTML/SQL escaping
✓ CSS-in-JS libraries
✓ Query builders
✓ i18n systems
✓ DSL creation
Patterns:
✓ Return transformed strings
✓ Return structured objects
✓ Chain multiple tags
✓ Cache expensive operations
Performance:
✓ strings array is cached by engine
✓ Use Map for result caching
✓ Avoid heavy computation in tags
✓ Consider lazy evaluation
Avoid:
✗ Side effects in tags
✗ Mutating the strings array
✗ Ignoring strings.raw when needed
✗ Over-complex transformations
Conclusion
Tagged template literals enable powerful string processing by separating static strings from dynamic values. Use them for safe HTML/SQL escaping, building DSLs, creating CSS-in-JS solutions, and implementing i18n systems. The tag function receives the template parts separately, allowing custom processing, validation, and transformation while maintaining clean syntax at the call site.