A dynamic string class for optimal text manipulation

• Array-like flexibility to control strings

• Significantly faster than JS string concatenation and split Array handling

• Automatic memory management with ability to allocate or shrink space as needed

• Convenient API

  • negative indices behave like Python
  • extends the String interface (work in-progress)
  • documentation available

• Best Use Cases

  • handling large streams of text
  • altering large files

Main repository hosted on GitHub.

Tools

Interest in StringBuilder

JavaScript strings are immutable primitives that create garbage for every unique sequence generated via concatenation, slicing, etc.

StringBuilder attempts to provide an efficient way to dynamically build JavaScript strings, friendly toward the garbage collector.

Installation

Build JavaScript file

with yarn:

yarn install
yarn build

with npm:

npm i
npm run build

Example Usage

Create a StringBuilder string

// Set initial character length if you know its size ahead of time,
const stringBuilder = new StringBuilder(1000000);

// or later via `reserve`.
stringBuilder.reserve(1000000);

// Efficient for lots of appending,
for (let i = 0; i < 1000000; ++i)
    stringBuilder.append((i % 10).toString());

// then retrieve the final value.
let str = stringBuilder.str(); // "01234567890123..."

Insertion and deletion via splice

const stringBuilder = new StringBuilder("01234");

stringBuilder.splice(0, 1, "abc");

let str = stringBuilder.str(); // "0abc234"

Find & replace

const stringBuilder = new StringBuilder("Hello world!");

// mutates internal string
stringBuilder.replace(/world/, "StringBuilder");

console.log(stringBuilder.str()); // "Hello StringBuilder!"

Documentation

Hosted here: https://code.aaronishibashi.com/js-stringbuilder

Performance Comparison

	StringBuilder	String	Array<string>
500,000 char appends	5.26ms	22.55ms	17.65ms
500,000 mid-insertions	2,465.29ms	20,761.87ms	9,658.66ms
500,000 char prepends	7.38ms	25.65ms	19,334.63ms

	StringBuilder	String	Array<string>
1 million char appends	6.90ms	51.77ms	30.11ms
1 million mid-insertions	9,735.18ms	72,645.41ms	88,937.65ms
1 million char prepends	38.18ms	52.75ms	80,454.23ms

These metrics were tested in Node v20.3.1 on an ARM MacOS 13.

To run the tests on your own machine use: yarn test:perf or npm run test:perf

Please let me know if there is any performance issue on your system :-)

Roadmap

• search
• incorporate regexp
• documentation
• implement replaceAll
• extensive testing