Add binary option

index.d.ts

@@ -20,9 +20,9 @@ declare namespace prettyBytes {
 
 		/**
 		Format the number as [bits](https://en.wikipedia.org/wiki/Bit) instead of [bytes](https://en.wikipedia.org/wiki/Byte). This can be useful when, for example, referring to [bit rate](https://en.wikipedia.org/wiki/Bit_rate).
-		
+
 		@default false
-		
+
 		```
 		import prettyBytes = require('pretty-bytes');
 
@@ -31,6 +31,23 @@ declare namespace prettyBytes {
 		```
 		*/
 		readonly bits?: boolean;
+
+		/**
+		Format the number using the [Binary Prefix](https://en.wikipedia.org/wiki/Binary_prefix) instead of the [SI Prefix](https://en.wikipedia.org/wiki/SI_Prefix). This can be useful for presenting memory amounts. However, this should not be used for presenting file sizes.
+
+		@default false
+
+		```
+		import prettyBytes = require('pretty-bytes');
+
+		prettyBytes(1000, {binary: true});
+		//=> '1000 bit'
+
+		prettyBytes(1024, {binary: true});
+		//=> '1 kiB'
+		```
+		*/
+		readonly binary?: boolean;
 	}
 }
 

index.js

@@ -12,6 +12,18 @@ const BYTE_UNITS = [
 	'YB'
 ];
 
+const BIBYTE_UNITS = [
+	'B',
+	'kiB',
+	'MiB',
+	'GiB',
+	'TiB',
+	'PiB',
+	'EiB',
+	'ZiB',
+	'YiB'
+];
+
 const BIT_UNITS = [
 	'b',
 	'kbit',
@@ -46,8 +58,8 @@ module.exports = (number, options) => {
 		throw new TypeError(`Expected a finite number, got ${typeof number}: ${number}`);
 	}
 
-	options = Object.assign({bits: false}, options);
-	const UNITS = options.bits ? BIT_UNITS : BYTE_UNITS;
+	options = Object.assign({bits: false, binary: false}, options);
+	const UNITS = options.bits ? (options.binary ? BIBYTE_UNITS : BIT_UNITS) : BYTE_UNITS;
 
 	if (options.signed && number === 0) {
 		return ' 0 ' + UNITS[0];
@@ -65,9 +77,9 @@ module.exports = (number, options) => {
 		return prefix + numberString + ' ' + UNITS[0];
 	}
 
-	const exponent = Math.min(Math.floor(Math.log10(number) / 3), UNITS.length - 1);
+	const exponent = Math.min(Math.floor(options.binary ? Math.log(number) / Math.log(1024) : Math.log10(number) / 3 ), UNITS.length - 1);
 	// eslint-disable-next-line unicorn/prefer-exponentiation-operator
-	number = Number((number / Math.pow(1000, exponent)).toPrecision(3));
+	number = Number((number / Math.pow(options.binary ? 1024 : 1000, exponent)).toPrecision(3));
 	const numberString = toLocaleString(number, options.locale);
 
 	const unit = UNITS[exponent];

index.test-d.ts

@@ -8,3 +8,4 @@ expectType<string>(prettyBytes(42, {signed: true}));
 expectType<string>(prettyBytes(1337, {locale: 'de'}));
 expectType<string>(prettyBytes(1337, {locale: true}));
 expectType<string>(prettyBytes(1337, {bits: true}));
+expectType<string>(prettyBytes(1337, {binary: true}));

test.js

@@ -82,3 +82,15 @@ test('bits option', t => {
 	t.is(prettyBytes(1e16, {bits: true}), '10 Pbit');
 	t.is(prettyBytes(1e30, {bits: true}), '1000000 Ybit');
 });
+
+test('binary option', t => {
+	t.is(prettyBytes(0, {binary: true}), '0 B');
+	t.is(prettyBytes(4, {binary: true}), '4 B');
+	t.is(prettyBytes(10, {binary: true}), '10 B');
+	t.is(prettyBytes(10.1, {binary: true}), '10.1 B');
+	t.is(prettyBytes(999, {binary: true}), '999 B');
+	t.is(prettyBytes(1025, {binary: true}), '1 kB');
+	t.is(prettyBytes(1001, {binary: true}), '1000 B');
+	t.is(prettyBytes(1e16, {binary: true}), '8.88 PB');
+	t.is(prettyBytes(1e30, {binary: true}), '827000 YB');
+});