sed-lite

1.1.0 verified Fri May 01 auth: no javascript

JavaScript implementation of the sed command-line tool for text substitution. Current stable version 1.1.0 compiles sed expressions to functions, supporting flags like g (global) and custom delimiters. The library is lightweight, has no dependencies, and ships TypeScript declarations. It differs from alternatives like xregexp by focusing on sed syntax compatibility, enabling use in Node.js and browsers.

Common errors

error SyntaxError: Invalid regular expression: /s/(foo)/(bar)//: Nothing to repeat ↓

cause Passing a sed command string with slashes without proper escaping or incorrect syntax.

fix

Ensure the sed string is correctly formatted: e.g., 's/foo/bar/' — use valid JavaScript RegExp patterns. If using custom delimiter, use a character not appearing in the pattern or replacement, e.g., 's#foo#bar#'.

error TypeError: sed is not a function ↓

cause Incorrect import: default import vs named import mismatch.

fix

Use import { sed } from 'sed-lite' (named) or import sed from 'sed-lite' (default), depending on how you want to call it.

error sed(...) is not a function ↓

cause sed() returns a function that takes a string argument. Using it directly as a replacement function (e.g., String.prototype.replace(sed(...))) is invalid.

fix

Call sed(expression)(input) or store the compiled function in a variable.

Warnings

gotcha sed-lite does not support all GNU sed features; only 's' command (substitute) is implemented. Attempting other commands like 'd', 'p', 'a', 'i' may throw or silently fail. ↓

fix Use only 's' command. For extended functionality, consider other libraries like xregexp or manual RegExp.

gotcha Regular expression syntax follows JavaScript RegExp, not sed's BRE/ERE. Escaping patterns may differ from standard sed (e.g., back-references use $1 instead of \1). ↓

fix Use JavaScript regex syntax: e.g., 's/(\w+)/$1/' — note the double escaping in string literal.

gotcha Flags other than 'g' (global) are not supported (e.g., 'i' for case-insensitive, flags for multiple replacement with 'N' substitution). Attempting unknown flags may be ignored or cause unexpected behavior. ↓

fix To mimic 'i' flag, modify regex pattern manually: e.g., 's/pattern/replacement/i' in string but sed-lite does not interpret 'i'. Instead use native RegExp: str.replace(/pattern/i, 'replacement').

deprecated The package exports a default function and named 'sed'. The default export may be deprecated in future; prefer named import. ↓

fix Use import { sed } from 'sed-lite' instead of import sed from 'sed-lite'.

Install

npm install sed-lite

yarn add sed-lite

pnpm add sed-lite

Imports

sed
wrong
```
const { sed } = require('sed-lite')
```
correct
```
import { sed } from 'sed-lite'
```
ESM module; require() may work in Node, but ESM import is preferred.

default

wrong

import { sed } from 'sed-lite' // if default export is used

correct

import sed from 'sed-lite'

sed-lite also exports a default function; both patterns work.

SedExpression
```
import type { SedExpression } from 'sed-lite'
```
TypeScript type for compiled sed function. Not required at runtime.

Quickstart

Demonstrates basic usage: compile sed substitution, global flag, custom delimiter, and chaining expressions.

import { sed } from 'sed-lite';

const transform = sed('s/world/JavaScript/');
const result = transform('Hello, world!');
console.log(result); // Hello, JavaScript!

// With global flag
const replaceAll = sed('s/\d+/###/g');
console.log(replaceAll('Item 1, Item 2, Item 3')); // Item ###, Item ###, Item ###

// Custom delimiter
const changeFormat = sed('s#2024-01-01#01/01/2024#');
console.log(changeFormat('Date: 2024-01-01')); // Date: 01/01/2024

// Chain multiple expressions with semicolon
const multi = sed('s/foo/bar/; s/bar/baz/');
console.log(multi('foo')); // baz