Replace in file

A simple utility to quickly replace text in one or more files or globs. Works synchronously or asynchronously with either promises or callbacks. Make a single replacement or multiple replacements at once.

Index

Installation
Basic usage
Advanced usage
CLI usage
A note on using globs with the CLI
Version information
License

Installation

# Using npm
npm i replace-in-file

# Using yarn
yarn add replace-in-file

Asynchronous replacement

import {replaceInFile} from 'replace-in-file'

const options = {
  files: 'path/to/file',
  from: /foo/g,
  to: 'bar',
}

try {
  const results = await replaceInFile(options)
  console.log('Replacement results:', results)
}
catch (error) {
  console.error('Error occurred:', error)
}

Synchronous replacement

import {replaceInFileSync} from 'replace-in-file'

const options = {
  files: 'path/to/file',
  from: /foo/g,
  to: 'bar',
}

try {
  const results = replaceInFileSync(options)
  console.log('Replacement results:', results)
}
catch (error) {
  console.error('Error occurred:', error)
}

Return value

The return value of the library is an array of replacement results against each file that was processed. This includes files in which no replacements were made.

Each result contains the following values:

file: The path to the file that was processed
hasChanged: Flag to indicate if the file was changed or not

const results = replaceInFileSync({
  files: 'path/to/files/*.html',
  from: /foo/g,
  to: 'bar',
})

console.log(results)

// [
//   {
//     file: 'path/to/files/file1.html',
//     hasChanged: true,
//   },
//   {
//     file: 'path/to/files/file2.html',
//     hasChanged: true,
//   },
//   {
//     file: 'path/to/files/file3.html',
//     hasChanged: false,
//   },
// ]

To get an array of changed files, simply map the results as follows:

const changedFiles = results
  .filter(result => result.hasChanged)
  .map(result => result.file)

Counting matches and replacements

By setting the countMatches configuration flag to true, the number of matches and replacements per file will be counted and present in the results array.

numMatches: Indicates the number of times a match was found in the file
numReplacements: Indicates the number of times a replacement was made in the file

Note that the number of matches can be higher than the number of replacements if a match and replacement are the same string.

const results = replaceInFileSync({
  files: 'path/to/files/*.html',
  from: /foo/g,
  to: 'bar',
  countMatches: true,
})

console.log(results)

// [
//   {
//     file: 'path/to/files/file1.html',
//     hasChanged: true,
//     numMatches: 3,
//     numReplacements: 3,
//   },
//   {
//     file: 'path/to/files/file2.html',
//     hasChanged: true,
//     numMatches: 1,
//     numReplacements: 1,
//   },
//   {
//     file: 'path/to/files/file3.html',
//     hasChanged: false,
//     numMatches: 0,
//     numReplacements: 0,
//   },
// ]

Advanced usage

Replace a single file or glob

const options = {
  files: 'path/to/file',
}

Replace multiple files or globs

const options = {
  files: [
    'path/to/file',
    'path/to/other/file',
    'path/to/files/*.html',
    'another/**/*.path',
  ],
}

Replace first occurrence only

const options = {
  from: 'foo',
  to: 'bar',
}

Replace all occurrences

Please note that the value specified in the from parameter is passed straight to the native String replace method. As such, if you pass a string as the from parameter, it will only replace the first occurrence.

To replace multiple occurrences at once, you must use a regular expression for the from parameter with the global flag enabled, e.g. /foo/g.

const options = {
  from: /foo/g,
  to: 'bar',
}

Multiple values with the same replacement

These will be replaced sequentially.

const options = {
  from: [/foo/g, /baz/g],
  to: 'bar',
}

Multiple values with different replacements

These will be replaced sequentially.

const options = {
  from: [/foo/g, /baz/g],
  to: ['bar', 'bax'],
}

Multiple replacements with different options

There is no direct API in this package to make multiple replacements on different files with different options. However, you can easily accomplish this in your scripts as follows:

const replacements = [
  {
    files: 'path/to/file1',
    from: /foo/g,
    to: 'bar',
  },
  {
    files: 'path/to/file2',
    from: /bar/g,
    to: 'foo',
  }
]

await Promise.all(
  replacements.map(options => replaceInFile(options))
)

Custom regular expressions

Use the RegExp constructor to create any regular expression.

const str = 'foo'
const regex = new RegExp('^' + str + 'bar', 'i')
const options = {
  from: regex,
  to: 'bar',
}

Using callbacks for `from`

You can also specify a callback that returns a string or a regular expression. The callback receives the name of the file in which the replacement is being performed, thereby allowing the user to tailor the search string. The following example uses a callback to produce a search string dependent on the filename:

const options = {
  files: 'path/to/file',
  from: (file) => new RegExp(file, 'g'),
  to: 'bar',
}

Using callbacks for `to`

As the to parameter is passed to the native String replace method, you can also specify a callback. The following example uses a callback to convert matching strings to lowercase:

const options = {
  files: 'path/to/file',
  from: /SomePattern[A-Za-z-]+/g,
  to: (match) => match.toLowerCase(),
}

This callback provides for an extra argument above the String replace method, which is the name of the file in which the replacement is being performed. The following example replaces the matched string with the filename:

const options = {
  files: 'path/to/file',
  from: /SomePattern[A-Za-z-]+/g,
  to: (...args) => args.pop(),
}

Saving to a different file

You can specify a getTargetFile config param to modify the target file for saving the new file contents to. For example:

const options = {
  files: 'path/to/files/*.html',
  getTargetFile: source => `new/path/${source}`,
  from: 'foo',
  to: 'bar',
}

Ignore a single file or glob

const options = {
  ignore: 'path/to/ignored/file',
}

Ignore multiple files or globs

const options = {
  ignore: [
    'path/to/ignored/file',
    'path/to/other/ignored_file',
    'path/to/ignored_files/*.html',
    'another/**/*.ignore',
  ],
}

Please note that there is an open issue with Glob that causes ignored patterns to be ignored when using a ./ prefix in your files glob. To work around this, simply remove the prefix, e.g. use **/* instead of ./**/*.

Allow empty/invalid paths

If set to true, empty or invalid paths will fail silently and no error will be thrown. For asynchronous replacement only. Defaults to false.

const options = {
  allowEmptyPaths: true,
}

Disable globs

You can disable globs if needed using this flag. Use this when you run into issues with file paths like files like //SERVER/share/file.txt. Defaults to false.

const options = {
  disableGlobs: true,
}

Specify glob configuration

Specify configuration passed to the glob call:

const options = {

  //Glob settings here (examples given below)
  glob: {

    //To include hidden files (starting with a dot)
    dot: true,

    //To fix paths on Windows OS when path.join() is used to create paths
    windowsPathsNoEscape: true,
  },
}

Please note that the setting nodir will always be passed as false.

Making replacements on network drives

To make replacements in files on network drives, you may need to specify the UNC path as the cwd config option. This will then be passed to glob and prefixed to your paths accordingly. See #56 for more details.

Specify character encoding

Use a different character encoding for reading/writing files. Defaults to utf-8.

const options = {
  encoding: 'utf8',
}

Dry run

To do a dry run without actually making replacements, for testing purposes. Defaults to false.

const options = {
  dry: true,
}

Using custom processors

For advanced usage where complex processing is needed it's possible to use a callback that will receive content as an argument and should return it processed.

const results = await replaceInFile({
  files: 'path/to/files/*.html',
  processor: (input) => input.replace(/foo/g, 'bar'),
})

The custom processor will receive the path of the file being processed as a second parameter:

const results = await replaceInFile({
  files: 'path/to/files/*.html',
  processor: (input, file) => input.replace(/foo/g, file),
})

This also supports passing an array of functions that will be executed sequentially

function someProcessingA(input) {
  const chapters = input.split('###')
  chapters[1] = chapters[1].replace(/foo/g, 'bar')
  return chapters.join('###')
}

function someProcessingB(input) {
  return input.replace(/foo/g, 'bar')
}

const results = replaceInFileSync({
  files: 'path/to/files/*.html',
  processor: [someProcessingA, someProcessingB],
})

Alongside the processor, there is also processorAsync which is the equivalent for asynchronous processing. It should return a promise that resolves with the processed content:

const results = await replaceInFile({
  files: 'path/to/files/*.html',
  processorAsync: async (input, file) => {
    const asyncResult = await doAsyncOperation(input, file);
    return input.replace(/foo/g, asyncResult)
  },
})

Using a custom file system API

replace-in-file defaults to using 'node:fs/promises' and 'node:fs' to provide file reading and write APIs. You can provide an fs or fsSync object of your own to switch to a different file system, such as a mock file system for unit tests.

For the asynchronous APIs, the provided fs must provide the readFile and writeFile methods.
For the synchronous APIs, the provided fsSync must provide the readFileSync and writeFileSync methods.

Custom fs and fsSync implementations should have the same parameters and returned values as their built-in Node fs equivalents.

replaceInFile({
  from: 'a',
  fs: {
    readFile: async (file, encoding) => {
      console.log(`Reading ${file} with encoding ${encoding}...`)
      return 'fake file contents'
    },
    writeFile: async (file, newContents, encoding) => {
      console.log(`Writing ${file} with encoding ${encoding}: ${newContents}`)
    },
  },
  to: 'b',
})

Or for the sync API:

replaceInFileSync({
  from: 'a',
  fsSync: {
    readFileSync: (file, encoding) => {
      console.log(`Reading ${file} with encoding ${encoding}...`)
      return 'fake file contents'
    },
    writeFileSync: (file, newContents, encoding) => {
      console.log(`Writing ${file} with encoding ${encoding}: ${newContents}`)
    },
  },
  to: 'b',
})

CLI usage

replace-in-file from to some/file.js,some/**/glob.js
  [--configFile=config.json]
  [--ignore=ignore/files.js,ignore/**/glob.js]
  [--encoding=utf-8]
  [--disableGlobs]
  [--verbose]
  [--quiet]
  [--dry]

Multiple files or globs can be replaced by providing a comma separated list.

The flags --disableGlobs, --ignore and --encoding are supported in the CLI.

The setting allowEmptyPaths is not supported in the CLI as the replacement is synchronous, and this setting is only relevant for asynchronous replacement.

To list the changed files, use the --verbose flag. Success output can be suppressed by using the --quiet flag.

To do a dry run without making any actual changes, use --dry.

A regular expression may be used for the from parameter by passing in a string correctly formatted as a regular expression. The library will automatically detect that it is a regular expression.

The from and to parameters, as well as the files list, can be omitted if you provide this information in a configuration file.

You can provide a path to a configuration file (JSON) with the --configFile flag. This path will be resolved using Node’s built in path.resolve(), so you can pass in an absolute or relative path.

If you are using a configuration file, and you want to use a regular expression for the from value, ensure that it starts with a /, for example:

{
  "from": "/cat/g",
  "to": "dog",
}

A note on using globs with the CLI

When using the CLI, the glob pattern is handled by the operating system. But if you specify the glob pattern in the configuration file, the package will use the glob module from the Node modules, and this can lead to different behaviour despite using the same pattern.

For example, the following will only look at top level files:

{
  "from": "cat",
  "to": "dog",
}

replace-in-file **  --configFile=config.json

However, this example is recursive:

{
  "files": "**",
  "from": "cat",
  "to": "dog",
}

replace-in-file --configFile=config.json

If you want to do a recursive file search as an argument you must use:

replace-in-file $(ls l {,**/}*)  --configFile=config.json

Version information

From version 8.0.0 onwards, this package requires Node 18 or higher. If you need support for older versions of Node, please use a previous version of this package.

As 8.0.0 was a significant rewrite, please open an issue if you run into any problems or unexpected behaviour.

See the Changelog for more information.

License

(MIT License)

Name		Name	Last commit message	Last commit date
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.yarn		.yarn
bin		bin
src		src
types		types
.c8rc		.c8rc
.editorconfig		.editorconfig
.gitattributes		.gitattributes
.gitignore		.gitignore
.yarnrc.yml		.yarnrc.yml
CHANGELOG.md		CHANGELOG.md
README.md		README.md
eslint.config.js		eslint.config.js
index.js		index.js
package.json		package.json
yarn.lock		yarn.lock

adamreisnz/replace-in-file

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