srTokens

npm package: string-range-tokens

Turn any string into a letter-per-index token array, then rebuild words, paths or URLs from index ranges.

Zero dependencies, plain ESM, works in Node 18+ and the browser. Ships a JavaScript implementation, a TypeScript implementation and type definitions.

Install

npm i string-range-tokens

Or copy src/index.js (or src/index.ts) into your project. No build step.

JavaScript and TypeScript

// JavaScript (types come for free via index.d.ts)
import { toTokens, sub } from 'string-range-tokens';

// TypeScript
import { toTokens, sub, type Range } from 'string-range-tokens';

const ranges: Range[] = [[26, 31]];
sub(toTokens('https://api.example.com/v1/users'), 23, 25, ...ranges);

The TypeScript source lives in src/index.ts and is also exported as string-range-tokens/ts for runtimes that run TS directly (Deno, Bun, Node with type stripping).

CDN: jsdelivr

  import { toTokens, sub, build, plan, scatter, gather } from 'https://cdn.jsdelivr.net/npm/[email protected]/src/index.js';

Usage

import { toTokens, sub, build, plan, scatter, gather } from 'string-range-tokens';

const t = toTokens('https://api.example.com/v1/users');

sub(t, 0, 4);                 // "https"
sub(t, 23, 25, [26, 31]);     // "/v1/users"
sub(t, -5, -1);               // "users"
build(t, [0, 4], [23, 25]);   // "https/v1"

API

| Function | What it does | | --- | --- | | toTokens(str) | String to array of single characters (unicode safe) | | sub(tokens, start, end, ...[s, e]) | Join inclusive ranges. Negative indexes count from the end. [i] picks one token | | build(tokens, ...[s, e]) | Same, ranges only. No ranges returns the whole string | | plan(tokens, target) | Finds ranges that rebuild target from the tokens | | scatter(str, seed) | Seeded shuffle, returns { pool, key } | | gather(pool, key) | Rebuilds the string from scatter output |

Build a word from a pool of letters

const pool = toTokens('the quick brown fox');
const ranges = plan(pool, 'brew');
build(pool, ...ranges); // "brew"

Scatter and gather

const { pool, key } = scatter('/api/orders', 7);
gather(pool, key); // "/api/orders"

Use cases

• Assemble API paths and keys from shared token pools
• Pick substrings by position without regex
• Tiny string templating from a fixed alphabet
• Teaching and puzzles around indexing and recursion

Security note

This is string assembly, not encryption. Anything shipped to a browser can be read by the user. Never hide real secrets or API keys with it. Keep them server side (Netlify Functions, Workers, etc).

Test

npm test

Contributing

See CONTRIBUTING.md.

License

MIT, see LICENSE.