@prelude/string

A TypeScript library for string manipulation with functional programming principles.

Core Functions

• isBlank: (value: string) => boolean

  Returns true if provided string is blank, false otherwise.

• ifBlank: <T>(value: string, thenThunk: () => T) => string | T

  Maps blank string to arbitrary value. Returns value as is if not blank.

• dedent: (value: string) => string

  Returns string lines without shared indentation.

• firstIndent: (value: string) => string

  Returns first line's indent.

• indentTail: (value: string, indent?: string) => string

  Returns string with all lines but the first one indented.

• indent: (value: string, indent_?: string) => string

  Returns string lines prefixed with provided indentation.

String Transformations

• upperFirst: (value: string) => string

  Returns the provided string with the first character as upper case.

• truncate: (str: string, length: number, suffix?: string) => string

  Truncates a string to the specified length and adds a suffix if truncated.

• searchReplace: (source: string, search: string, replacement: string) => string

  Fuzzy search and replace functionality.

Case Conversions

• camelCase: (str: string) => string

  Converts a string to camelCase.

• kebabCase: (str: string) => string

  Converts a string to kebab-case.

• snakeCase: (str: string) => string

  Converts a string to snake_case.

• startCase: (str: string) => string

  Converts a string to Start Case.

String Distance

• distance: (a: string, b: string, method?: 'levenshtein') => number

  Calculate the distance between two strings using the specified method.

Lines Module

The library exports a Lines namespace with functions for working with string lines:

• Lines.of: (value: string) => string[]

  Splits a string into an array of lines, handling different line endings.

• Lines.similarIndexOf: (sourceLines: string[], searchLines: string[]) => number

  Finds most similar index in source lines for search lines, useful for fuzzy text search.

• Lines.distanceAt: (sourceLines: string[], at: number, queryLines: string[], distanceOf?) => number

  Calculate the similarity score between query and source lines at a given index.

• Lines.indent: (mutableLines: string[], indentation?: string) => void

  Mutably indents each line in the array with the specified indentation.

• Lines.toIndent: (lines: string[], indentation?: string) => string[]

  Returns a new array of lines with the specified indentation.

Lines.Diff - Text Diffing Utilities

The Lines module includes powerful diffing capabilities:

• Lines.Diff.myers: (sourceLines: string[], targetLines: string[]) => Op[]

  Calculates diff between two sets of lines using the Myers algorithm.

• Lines.Diff.histogram: (sourceLines: string[], targetLines: string[]) => Op[]

  Performs histogram-based diff optimized for performance on large inputs.

• Lines.Diff.Op - Operations API for working with diff results:

  • type Op.T - Diff operation type: { type: 'unchanged' | 'removed' | 'added', lines: string[] }
  • Op.append - Appends operations at the end of diff ops
  • Op.prepend - Prepends operations at the beginning of diff ops
  • Op.verify - Verifies that ops applied to the source produce target
  • Op.readable - Maps ops to readable strings with prefixes
  • Op.dump - Produces a full debug dump of source, target, and operations

Usage

npm i -E @prelude/string
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import * as S from '@prelude/string'
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License

This package is dedicated to the public domain under CC0 1.0.