README.md

string-differ

Description

A zero-dependency library to compare and transform strings. This library can:

• Generate operations to convert one string to another string.
• Apply a given set of operations to a string to transform it into another string.

Installation

npm i string-differ

Usage

This library uses a linear space implementation of Myers diff algorithm to calculate the shortest edit script between two strings. It assumes that a string can be converted to another using 3 types of operations:

• insertion
• retention
• deletion

These types describe the operations that can be performed on string s1 to convert it to string s2. Consecutive operations of the same type are grouped together.

Generate Steps for Conversion

import { getStepsForTransformation } from 'string-differ';

const s1 = 'initial string';
const s2 = 'final string';

const steps = getStepsForTransformation({ s1, s2 });

console.log(steps);

will output:

[
  { type: 'delete', value: 'ini' },
  { type: 'insert', value: 'fin' },
  { type: 'delete', value: 't' },
  { type: 'delete', value: 'i' },
  { type: 'retain', value: 'al string' }
]

For all operations, the value field contains the relevant substring. For delete and retain, it's the substring from s1. For insert, it's the substring to be inserted from s2.

Apply Operations to a String

Given a set of operations, the transformString function can be used to apply the steps to get the resultant string s2.

import { transformString } from 'string-differ';

const operations = [
  { type: 'delete', value: 'ini' },
  { type: 'insert', value: 'fin' },
  { type: 'delete', value: 't' },
  { type: 'delete', value: 'i' },
  { type: 'retain', value: 'al string' }
];

const s2 = transformString(operations);
console.log(s2);

will output:

'final string'

License

This library is distributed under the LGPL-3.0 License. See LICENSE for more information.