string-masking

string-masking

This package masks strings in two ways:

• Legacy digit mode for the original package behavior.
• Options-based mode for cleaner masking with support for formatted strings.

What This Repository Does

The repository exports a single function from index.js:

const stringMask = require("string-masking");

It returns a model in this shape:

{
  status: "success" | "failure",
  response: "masked output or error message"
}

Failures also include a NOTE field.

Legacy API

Keep the last N characters visible

const stringMask = require("string-masking");

const output = stringMask("1234567890", 3);
console.log(output);

// { status: 'success', response: 'XXXXXXX890' }

Keep the first N characters visible

const stringMask = require("string-masking");

const output = stringMask("1234567890", -3);
console.log(output);

// { status: 'success', response: '123XXXXXXX' }

Mask the middle portion

const stringMask = require("string-masking");

const output = stringMask("1234567890", 0);
console.log(output);

// { status: 'success', response: '12XXXXXX90' }

Improved API

Use an options object when you want more control.

Keep a custom number of characters at the start and end

const stringMask = require("string-masking");

const output = stringMask("ABCD1234EFGH", {
  visibleStart: 2,
  visibleEnd: 2
});

console.log(output);

// { status: 'success', response: 'ABXXXXXXXXGH' }

Preserve separators such as spaces, dashes, and symbols

const stringMask = require("string-masking");

const output = stringMask("4111-1111-1111-1111", {
  visibleEnd: 4,
  preserveFormat: true
});

console.log(output);

// { status: 'success', response: 'XXXX-XXXX-XXXX-1111' }

Mask alternate characters

const stringMask = require("string-masking");

const output = stringMask("ABCDEFGH", {
  alternateMask: true
});

console.log(output);

// { status: 'success', response: 'XBXDXFXH' }

Use the legacy digit argument with formatting support

const stringMask = require("string-masking");

const output = stringMask("ABHA-9988-XY12", 4, {
  preserveFormat: true,
  maskChar: "*"
});

console.log(output);

// { status: 'success', response: '****-****-XY12' }

Options

Option	Type	Default	Description
visibleStart	integer	0	Number of maskable characters to keep visible at the start
visibleEnd	integer	0	Number of maskable characters to keep visible at the end
preserveFormat	boolean	false	Preserves non-alphanumeric separators while masking
maskChar	string	"X"	Single character used for masking
alternateMask	boolean	false	Masks every other eligible character inside the maskable region

When preserveFormat is true, letters and numbers are masked, while characters such as spaces, -, ., @, and + stay in place.

When alternateMask is true, alternating starts from the first character that would otherwise be masked after visibleStart and visibleEnd are applied.

Suggestions For Further Improvement

• Add TypeScript definitions so the options API is easier to consume in editors.
• Publish a major version when you want to formalize the new options-based API.
• Add a maskPattern option later if you want different masking rules for emails, phones, or IDs.
• Add CI to run npm test automatically before publishing.

Contribution

Rohan Solse
Suggestions and recommendations are welcome.
Contact: [e-mail]