jsdiffr

A faithful R port of the jsdiff JavaScript library. Compute differences between two pieces of text or two sequences at the level of characters, words, lines, sentences, CSS tokens, JSON values, or arbitrary arrays, using Myers' O(ND) difference algorithm. The core diff loop is implemented in C++ (via Rcpp) for speed on large inputs.

The output of every diff function matches jsdiff 9.0.0 exactly: the test suite checks > 4,000 randomly generated inputs against the real library.

Installation

Requires a C++ compiler (Rtools on Windows).

# install.packages("remotes")
remotes::install_github("KyleHaynes/anthropic_diff")

Quick start

library(jsdiffr)

diff_chars("the quick brown fox", "the quiet brown ox")

diff_words("The quick brown fox", "The slow brown fox")

diff_lines("alpha\nbeta\n", "alpha\nBETA\n")

Each function returns a data.table of change objects with columns value, added, removed, and count. Printing a diff colours additions green and deletions red.

HTML output and Shiny

diff_to_html() renders a diff as HTML spans (.jsdiff-added / .jsdiff-removed), and diff_css_default() returns matching CSS. This makes it easy to show a diff in an R Markdown report or a Shiny app.

diff_to_html(diff_words("the cat sat", "the dog sat"))
#> <div class="jsdiff"><pre class="jsdiff-pre">
#>   <span class="jsdiff-context">the </span>
#>   <span class="jsdiff-removed">cat</span>
#>   <span class="jsdiff-added">dog</span>
#>   <span class="jsdiff-context"> sat</span>
#> </pre></div>
#> (shown indented here for readability; the real output is a single line)

A minimal Shiny app that diffs two text areas:

library(shiny)
library(jsdiffr)

ui <- fluidPage(
  tags$head(tags$style(HTML(diff_css_default()))),
  titlePanel("jsdiffr live diff"),
  fluidRow(
    column(6, textAreaInput("old", "Old", "the quick brown fox\njumps over\n",
                            rows = 8, width = "100%")),
    column(6, textAreaInput("new", "New", "the slow brown fox\nleaps over\n",
                            rows = 8, width = "100%"))
  ),
  hr(),
  uiOutput("diff")
)

server <- function(input, output) {
  output$diff <- renderUI({
    HTML(diff_to_html(diff_lines(input$old, input$new)))
  })
}

shinyApp(ui, server)

A interactive Shiny app that diffs two text areas live:

library(shiny)
library(jsdiffr)

shiny::runApp(system.file("shiny/address_diff", package = "jsdiffr"))

Use diff_words() / diff_chars() instead of diff_lines() for word- or character-level highlighting.

Features

• Diffing: diff_chars, diff_words, diff_words_with_space, diff_lines, diff_trimmed_lines, diff_sentences, diff_css, diff_json, diff_arrays.
• Patches: structured_patch, create_patch, create_two_files_patch, format_patch, parse_patch, apply_patch, apply_patches, reverse_patch, plus Unix/Windows line-ending helpers.
• Converters: convert_changes_to_xml, convert_changes_to_dmp.
• Display: ANSI-coloured console printing and diff_to_html() for Shiny / R Markdown (with diff_css_default()).
• camelCase aliases (diffChars, createPatch, ...) for users porting JS.

Performance

A line diff of two 50,000-line files runs in about 0.25s; creating and applying the corresponding patch takes under a second combined.

Credits

Ported from jsdiff by Kevin Decker, which is distributed under the BSD 3-Clause license.