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min

Accepts numbers greater than or equal to the given minimum. 
function min(min: number, decoder?: Decoder<number>): Decoder<number>

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Parameters

  • min - The minimum acceptable value (inclusive)
  • decoder - Optional base decoder (defaults to number)

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Validation Rules

  • Value must be greater than or equal to min
  • Inherits validation from the base decoder

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Examples

import { min, integer } from 'decoders';

// Basic usage with default number decoder
const minTen = min(10);
minTen.decode(15);   // ✓ Ok(15)
minTen.decode(10);   // ✓ Ok(10)
minTen.decode(5);    // ✗ Error: "Too low, must be at least 10"

// Combine with integer decoder
const minTenInteger = min(10, integer);
minTenInteger.decode(15);    // ✓ Ok(15)
minTenInteger.decode(10.5);  // ✗ Error: "Number must be an integer"
minTenInteger.decode(5);     // ✗ Error: "Too low, must be at least 10"

// Negative minimum
const minNegative = min(-5);
minNegative.decode(-3);   // ✓ Ok(-3)
minNegative.decode(-10);  // ✗ Error: "Too low, must be at least -5"

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Use Cases

  • Age validation (minimum age requirement)
  • Minimum price or amount
  • Minimum quantity in stock
  • Rating systems with lower bounds

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max

Accepts numbers less than or equal to the given maximum. 
function max(max: number, decoder?: Decoder<number>): Decoder<number>

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Parameters

  • max - The maximum acceptable value (inclusive)
  • decoder - Optional base decoder (defaults to number)

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Validation Rules

  • Value must be less than or equal to max
  • Inherits validation from the base decoder

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Examples

import { max, integer } from 'decoders';

// Basic usage with default number decoder
const maxHundred = max(100);
maxHundred.decode(50);    // ✓ Ok(50)
maxHundred.decode(100);   // ✓ Ok(100)
maxHundred.decode(150);   // ✗ Error: "Too high, must be at most 100"

// Combine with integer decoder
const maxHundredInteger = max(100, integer);
maxHundredInteger.decode(50);     // ✓ Ok(50)
maxHundredInteger.decode(50.5);   // ✗ Error: "Number must be an integer"
maxHundredInteger.decode(150);    // ✗ Error: "Too high, must be at most 100"

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Use Cases

  • Maximum file size limits
  • Maximum price or budget
  • Percentage caps (e.g., max 100)
  • Rate limiting thresholds

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between

Accepts numbers within the given range (bounds are inclusive). 
function between(
  min: number,
  max: number,
  decoder?: Decoder<number>
): Decoder<number>

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Parameters

  • min - The minimum acceptable value (inclusive)
  • max - The maximum acceptable value (inclusive)
  • decoder - Optional base decoder (defaults to number)

​
Validation Rules

  • Value must be greater than or equal to min
  • Value must be less than or equal to max
  • Inherits validation from the base decoder

​
Examples

import { between, integer } from 'decoders';

// Basic usage with default number decoder
const range = between(1, 10);
range.decode(5);     // ✓ Ok(5)
range.decode(1);     // ✓ Ok(1)
range.decode(10);    // ✓ Ok(10)
range.decode(0);     // ✗ Error: "Too low, must be between 1 and 10"
range.decode(15);    // ✗ Error: "Too high, must be between 1 and 10"

// Combine with integer decoder for whole numbers only
const integerRange = between(1, 10, integer);
integerRange.decode(5);     // ✓ Ok(5)
integerRange.decode(5.5);   // ✗ Error: "Number must be an integer"
integerRange.decode(0);     // ✗ Error: "Too low, must be between 1 and 10"

// Percentage range
const percentage = between(0, 100);
percentage.decode(50.5);   // ✓ Ok(50.5)
percentage.decode(-5);     // ✗ Error: "Too low, must be between 0 and 100"

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Use Cases

  • Age ranges (e.g., 18-65)
  • Percentage values (0-100)
  • Rating systems (e.g., 1-5 stars)
  • Pagination limits
  • Temperature ranges
  • Port numbers (e.g., 1024-65535)

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Combining Range Decoders

All range decoders accept an optional base decoder parameter, allowing you to combine range constraints with type constraints: 
import { between, min, max, integer, positiveInteger } from 'decoders';

// Whole numbers between 1 and 100
const count = between(1, 100, integer);

// Non-negative integers with a minimum
const quantity = min(1, positiveInteger);

// Integer port number in valid range
const port = between(1024, 65535, integer);

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Composing Multiple Constraints

You can chain range decoders for complex validations: 
import { min, integer } from 'decoders';

// First ensure it's an integer, then apply minimum
const adultAge = min(18, integer);

// Or use between for both bounds at once
const validAge = between(0, 150, integer);

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