@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

import * as S from '@prelude/string'

License

This project is dedicated to the public domain under CC0 1.0 Universal (CC0 1.0) Public Domain Dedication.

To the extent possible under law, the authors listed in Authors.md have waived all copyright and related or neighboring rights to this software and associated documentation files.