Dynamic Mask

Dynamic masks allow the mask pattern to change or repeat during input. This is useful for inputs where the length or pattern can vary, like email addresses or variable-length numbers.

Basic Syntax

Use curly braces { } to define dynamic parts:

• {n} - Exactly n repetitions
• {n|j} - n repetitions with jit masking
• {n,m} - From n to m repetitions
• {n,m|j} - From n to m repetitions with jit masking
• {+} - One or more repetitions (starts from 1)
• {} - Zero or more repetitions (starts from 0)

Common Examples

Fixed Repetition

import { useMaskInput } from 'use-mask-input';

function FixedLengthInput() {
  const mask = useMaskInput({
    mask: 'aa-9{4}',
  });

  return (
    <input
      type="text"
      ref={mask}
      placeholder="AA-0000"
    />
  );
}

This mask requires exactly 4 digits after the letters.

Variable Length

function VariableLengthInput() {
  const mask = useMaskInput({
    mask: '9{1,10}',
  });

  return (
    <input
      type="text"
      ref={mask}
      placeholder="0"
    />
  );
}

Accepts 1 to 10 digits.

Email Address

function EmailInput() {
  const emailMask = useMaskInput({
    mask: '*{1,20}[.*{1,20}][.*{1,20}][.*{1,20}]@*{1,20}[.*{2,6}][.*{1,2}]',
  });

  return (
    <input
      type="email"
      ref={emailMask}
      placeholder="user@example.com"
    />
  );
}

This creates a flexible email mask that accepts:

• Local part: 1-20 alphanumeric characters
• Optional subdomains: up to 3 levels
• Domain: 1-20 alphanumeric characters
• TLD: 2-6 characters with optional country code

One or More Characters

function OneOrMoreInput() {
  const mask = useMaskInput({
    mask: 'A{+}',
  });

  return (
    <input
      type="text"
      ref={mask}
      placeholder="ABC"
    />
  );
}

Accepts one or more uppercase letters.

Zero or More Characters

function ZeroOrMoreInput() {
  const mask = useMaskInput({
    mask: '9{}',
  });

  return (
    <input
      type="text"
      ref={mask}
      placeholder="123"
    />
  );
}

Accepts zero or more digits.

Product Code

function ProductCodeInput() {
  const mask = useMaskInput({
    mask: 'A{2}-9{4,8}',
  });

  return (
    <input
      type="text"
      ref={mask}
      placeholder="AB-0000"
    />
  );
}

Requires 2 letters followed by 4 to 8 digits.

Flexible ID

function FlexibleIdInput() {
  const mask = useMaskInput({
    mask: 'ID-9{3,6}-A{1,3}',
  });

  return (
    <input
      type="text"
      ref={mask}
      placeholder="ID-000-ABC"
    />
  );
}

Accepts:

• ID-123-A
• ID-12345-ABC
• ID-123456-AB

JIT Masking

JIT (Just-In-Time) masking shows the mask only as the user types:

function JitMaskInput() {
  const mask = useMaskInput({
    mask: '9{4|1}',
    options: {
      jitMasking: true,
    },
  });

  return (
    <input
      type="text"
      ref={mask}
      placeholder="0"
    />
  );
}

Tips

• Use dynamic masks for inputs with variable lengths
• Combine with optional sections for maximum flexibility
• JIT masking provides a better user experience for long inputs
• Dynamic masks are perfect for email, URLs, and flexible ID formats