Telazer - NumberFormatter

For more helpers and utilities, check out the Telazer NPM Page

A TypeScript utility for compact, suffix-based number formatting with first-class BigInt support.

Installation

npm install @telazer/number-formatter

Key Features

• Works with both number and bigint
• String-slicing core – no floating-point drift, safe for very large values
• Flexible decimals: minDecimals, maxDecimals, forceDecimals, removeZeros
• Optional rounding modes (round, floor, ceil) – default is no rounding
• Custom suffix list (default: ["", "K", "M", "B", "T", "Q", "a"..."ah"])
• Convenient dual API:
  • bigNumberData() → structured parts
  • bigNumber() → final compact string

Quick Start

import { NumberFormatter } from '@telazer/number-formatter';

// String output
NumberFormatter.bigNumber(1500); // "1.5K"
NumberFormatter.bigNumber(1000, { minDecimals: 2 }); // "1.00K"
NumberFormatter.bigNumber(1999, { maxDecimals: 1 }); // "1.9K" (no rounding by default)
NumberFormatter.bigNumber(1500n, { forceDecimals: 3, maxDecimals: 3 }); // "1.500K"

// Structured output
const data = NumberFormatter.bigNumberData(1234567);
/// { input: 1234567, value: "1", decimals: "23", suffix: "M" }

API

bigNumberData(input, options?)

Returns structured parts for custom rendering.

type Numeric = number | bigint;

type NumberFormatData<T extends Numeric> = {
  input: T; // original input
  value: string; // "0".."999" (may include "-" for negatives)
  decimals: string; // fractional digits only ("" if none)
  suffix: string; // "", "K", "M", ...
};

bigNumber(input, options?)

Returns a single compact string assembled from the same parts: "${value}${decimals ? '.' + decimals : ''}${suffix}"

Options

type Rounding = 'round' | 'floor' | 'ceil';

type NumberFormatOptions<T extends number | bigint> = {
  minDecimals?: number; // default 0
  maxDecimals?: number; // default 2
  forceDecimals?: number; // exact decimals; pads/truncates to this length
  removeZeros?: boolean; // default true; trims trailing zeros beyond minDecimals
  rounding?: Rounding; // default undefined => NO rounding (truncate)
  suffixes?: readonly string[]; // custom suffix list
};

Defaults

{
  minDecimals: 0,
  maxDecimals: 2,
  forceDecimals: undefined,
  removeZeros: true,
  rounding: undefined,        // no rounding by default
  suffixes: ["", "K", "M", "B", "T", "Q", "a", "b", ..., "ah"]
}

Behavior Details

• No rounding by default Fractional digits are taken by slicing up to maxDecimals. Set rounding to enable rounding.

• minDecimals Ensures at least this many fractional digits by padding with zeros.

• maxDecimals Caps how many fractional digits are considered from the source.

• forceDecimals Overrides the above; pads or truncates to exactly this many digits.

• removeZeros When true (default), trailing zeros beyond minDecimals are trimmed. When false, the fractional part is padded to maxDecimals.

• Suffix selection Based on the integer digit length of the absolute input. Every group of 3 digits increases the suffix index. If a custom suffix list is short, scaling stops at its last entry and the integer part may exceed three digits. This is intentional.

• Numbers < 1000 No suffix. Decimal handling still applies.

• Decimal inputs (number) Normal values like 1.2424234 are supported. Extremely small/large JS numbers that stringify to exponential notation may need pre-normalization if you rely on precise fractional digits.

• Zero Respects minDecimals (e.g., 0 with { minDecimals: 2 } → "0.00").

• Negatives The sign is placed on the integer part only (e.g., -12_345 → "-12.34K").

Examples

// No rounding, just slicing
NumberFormatter.bigNumber(1999, { maxDecimals: 1 }); // "1.9K"

// Enable rounding
NumberFormatter.bigNumber(1201500, { maxDecimals: 1, rounding: 'round' }); // "1.2M"
NumberFormatter.bigNumber(1201500, { maxDecimals: 1, rounding: 'ceil' }); // "1.3M"
NumberFormatter.bigNumber(1201500, { maxDecimals: 1, rounding: 'floor' }); // "1.2M"

// Keep trailing zeros
NumberFormatter.bigNumber(1.2, { maxDecimals: 3, removeZeros: false }); // "1.200"

// Force exact decimals
NumberFormatter.bigNumber(1500, { forceDecimals: 3, maxDecimals: 3 }); // "1.500K"

// BigInt
NumberFormatter.bigNumber(12345678901234567890n, { maxDecimals: 6 }); // "12.345678a"

Custom Suffixes

const custom = ['', 'K', 'M']; // stop at 'M'
NumberFormatter.bigNumber(10n ** 60n, { suffixes: custom });
// Scales only to 'M'; leftover magnitude stays in the integer part.

Development

# Clone the repo
git clone https://github.com/Telazer/number-formatter

# Install dependencies
npm install

# Start the watcher for development
npm run watch

# Run tests
npm test

# Build the library
npm run build

License

MIT License

Copyright (c) 2025 Telazer

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.