realistic-typewriter

A small library for generating realistic typing event streams.

realistic-typewriter simulates human typing by yielding a stream of operations you can render using the method of your choice, such as DOM text or terminal output.

Installation

bun add realistic-typewriter

npm install realistic-typewriter

API

type KeyboardLayout = {
  getAdjacentCharacter(character: string): string | null;
};

type TypeOptions = {
  accuracy?: number;
  minSpeed?: number;
  maxSpeed?: number;
  layout?: KeyboardLayout;
};

type TypeEvent =
  | { kind: "wait"; ms: number }
  | { kind: "insert"; value: string }
  | { kind: "delete"; count: number };

declare function type(text: string, options?: TypeOptions): AsyncIterable<TypeEvent>;

TypeOptions

type TypeOptions = {
  accuracy?: number;
  minSpeed?: number;
  maxSpeed?: number;
  layout?: KeyboardLayout;
};

• accuracy: typing accuracy from 0 to 100, where higher values produce fewer typos
• minSpeed: minimum typing speed in characters per second
• maxSpeed: maximum typing speed in characters per second
• layout: keyboard layout used to generate adjacent-key typos

Events

type TypeEvent = WaitEvent | InsertEvent | DeleteEvent;

type WaitEvent = {
  kind: "wait";
  ms: number;
};

type InsertEvent = {
  kind: "insert";
  value: string;
};

type DeleteEvent = {
  kind: "delete";
  count: number;
};

WaitEvent

type WaitEvent = {
  kind: "wait";
  ms: number;
};

• emitted before the next visible typing action
• ms is the suggested delay in milliseconds

InsertEvent

type InsertEvent = {
  kind: "insert";
  value: string;
};

• appends visible text
• value is the string to insert

DeleteEvent

type DeleteEvent = {
  kind: "delete";
  count: number;
};

• removes previously rendered characters
• count is the number of characters to remove, usually 1

Usage

import { type } from "realistic-typewriter";

let output = "";

for await (const event of type("whoami", { accuracy: 95, minSpeed: 5, maxSpeed: 10 })) {
  if (event.kind === "wait") {
    await new Promise((resolve) => setTimeout(resolve, event.ms));
    continue;
  }

  if (event.kind === "insert") {
    output += event.value;
    continue;
  }

  output = output.slice(0, -event.count);
}

Built-in Layouts

qwerty is built in and used by default.

import { type } from "realistic-typewriter";
import { qwerty } from "realistic-typewriter/layouts";

for await (const event of type("hello", { layout: qwerty })) {
  // render events however you like
}

Custom Layouts

import { createKeyboardLayout } from "realistic-typewriter";

const layout = createKeyboardLayout([
  ["1", "2", "3"],
  ["Q", "W", "E"],
  ["A", "S", "D"],
]);

Development

The package ships dual ESM/CJS builds with Bun and uses Biome for linting and formatting.

bun install
bun run typecheck
bun run test
bun run build

License

Copyright (c) 2013 Fardjad Davari

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.