@ekaone/masker

Universal masking library — detects data type and applies appropriate masking automatically.

Zero dependencies. TypeScript-native. Works in Node.js, Deno, Bun, and the browser.

Features

• Auto-detection — mask(value) just works for 12 data types
• Explicit override — mask(value, { type: 'ssn' }) when you know the type
• Format-preserving — keeps spaces, dashes, @ symbols by default
• Configurable — custom mask char, reveal start/end counts
• Object helper — maskObject(obj) uses key name hints to bias detection
• Log sanitizer — maskString(text) scrubs tokens from free-form log lines
• TypeScript-native — full types, discriminated union results

Install

npm install @ekaone/masker
# or
pnpm add @ekaone/masker

Quick Start

import { mask, detect, maskObject, maskString } from "@ekaone/masker";

// Auto-detect and mask
mask("[email protected]");
// { masked: "jo*******@example.com", type: "email", confidence: 0.98 }

mask("4111 1111 1111 1111");
// { masked: "**** **** **** 1111", type: "credit_card", confidence: 0.92 }

mask("123-45-6789");
// { masked: "***-**-6789", type: "ssn", confidence: 0.97 }

mask("(415) 867-5309");
// { masked: "(***) ***-5309", type: "phone", confidence: 0.88 }

mask("192.168.100.42");
// { masked: "192.168.***.**, type: "ip_address", confidence: 0.93 }

mask("eyJhbGci....eyJzdWI....SflKxw...");
// {
//   original: 'eyJhbGci....eyJzdWI....SflKxw...',
//   masked: 'eyJh************************w...',
//   type: 'api_key',
//   confidence: 0.6
// }

Supported Types

| Type | Example input | Strategy | |-----------------|----------------------------|---------------------------------------| | email | [email protected] | Mask local part, keep domain | | phone | (415) 867-5309 | Mask all but last 4 digits | | credit_card | 4111 1111 1111 1111 | Mask all but last 4, preserve spaces | | ssn | 123-45-6789 | Mask all but last 4 | | ip_address | 192.168.100.42 | Mask last two octets | | url | https://api.io/v1?k=abc | Preserve host, mask path/query | | jwt | aaa.bbb.ccc | Keep header, mask payload + signature | | api_key | sk-proj-abc123XYZ | Reveal first/last 4 chars | | iban | GB29NWBK601613... | Reveal country + check digits only | | passport | AB1234567 | Reveal first 2 chars | | date_of_birth | 1990-07-15 | Reveal year only | | name | Margaret Thatcher | Reveal first letter of each word | | generic | anything else | Reveal first + last char |

API

mask(value, options?): MaskResult

Auto-detect or force-type and mask a string.

interface MaskOptions {
  type?: MaskType;        // force a specific type
  revealStart?: number;   // chars to show at start (type-dependent default)
  revealEnd?: number;     // chars to show at end
  char?: string;          // mask character (default: '*')
  preserveFormat?: boolean; // keep separators (default: true)
}

interface MaskResult {
  original: string;
  masked: string;
  type: MaskType;
  confidence: number;     // 0–1
}

detect(value): { type: MaskType; confidence: number }

Identify the data type without masking.

detect("[email protected]"); // { type: "email", confidence: 0.98 }

maskObject(obj, options?)

Mask all string fields in a plain object. Key name hints (e.g. email, ssn, token) bias the type detection.

maskObject({
  email: "[email protected]",
  phone: "555-123-4567",
  apiKey: "sk-abc123xyz456abc",
  age: 30,                      // non-strings are untouched
});
// {
//   email: 'al***@example.com',
//   phone: '***-***-4567',
//   apiKey: 'sk-a**********6abc',
//   age: 30
// }

maskString(text, options?)

Sanitize sensitive tokens found inside a free-form string. Useful for log scrubbing.

maskString("Request from [email protected] at 192.168.1.1 token=sk-abc123def456");
// "Request from us**@example.com at 192.168.*.* token=sk-a*******f456"

Options Examples

// Custom mask character
mask("123-45-6789", { char: "•" });
// "•••-••-6789"

// Custom reveal window
mask("sk-proj-abc123XYZ789", { revealStart: 6, revealEnd: 0 });
// "sk-pro*************"

// Disable format preservation
mask("4111 1111 1111 1111", { preserveFormat: false });
// "************1111"

License

MIT © Eka Prasetia

Links

• npm package
• GitHub repository
• Issue tracker