[feature suggestion] add roundingMethod option

README.md

@@ -53,6 +53,9 @@ _*(object)*_ Dictionary of SI/JEDEC/IEC symbols to replace for localization, def
 ### unix
 _*(boolean)*_ Enables unix style human readable output, e.g `ls -lh`, default is `false`
 
+### roundingMethod
+_*(string)*_ Rounding method, can be `round`, `floor`, or `ceil`, default is `round`
+
 ## Examples
 
 ```javascript

filesize.d.ts

@@ -94,6 +94,10 @@ declare namespace Filesize {
          *  Enables unix style human readable output, e.g ls -lh, default is false
          */
         unix?: boolean;
+        /**
+         * Rounding method, can be round, floor, or ceil, default is round
+         */
+        roundingMethod?: "round" | "floor" | "ceil";
     }
 
     interface Filesize {

lib/filesize.es6.js

@@ -25,6 +25,10 @@
 		fullform = {
 			iec: ["", "kibi", "mebi", "gibi", "tebi", "pebi", "exbi", "zebi", "yobi"],
 			jedec: ["", "kilo", "mega", "giga", "tera", "peta", "exa", "zetta", "yotta"]
+		},
+		roundingFuncs = {
+			floor: Math.floor,
+			ceil: Math.ceil
 		};
 
 	/**
@@ -38,7 +42,7 @@
 	function filesize (arg, descriptor = {}) {
 		let result = [],
 			val = 0,
-			e, base, bits, ceil, full, fullforms, locale, localeOptions, neg, num, output, pad, round, u, unix, separator, spacer, standard, symbols;
+			e, base, bits, ceil, full, fullforms, locale, localeOptions, neg, num, output, pad, round, u, unix, separator, spacer, standard, symbols, roundingFunc;
 
 		if (isNaN(arg)) {
 			throw new TypeError("Invalid number");
@@ -59,6 +63,7 @@
 		full = descriptor.fullform === true;
 		fullforms = descriptor.fullforms instanceof Array ? descriptor.fullforms : [];
 		e = descriptor.exponent !== void 0 ? descriptor.exponent : -1;
+		roundingFunc = roundingFuncs[descriptor.roundingMethod] || Math.round;
 		num = Number(arg);
 		neg = num < 0;
 		ceil = base > 2 ? 1000 : 1024;
@@ -102,7 +107,8 @@
 				}
 			}
 
-			result[0] = Number(val.toFixed(e > 0 ? round : 0));
+			const p = Math.pow(10, e > 0 ? round : 0);
+			result[0] = roundingFunc(val * p) / p;
 
 			if (result[0] === ceil && e < 8 && descriptor.exponent === void 0) {
 				result[0] = 1;

lib/filesize.js

@@ -25,6 +25,10 @@
 	    fullform = {
 	  iec: ["", "kibi", "mebi", "gibi", "tebi", "pebi", "exbi", "zebi", "yobi"],
 	  jedec: ["", "kilo", "mega", "giga", "tera", "peta", "exa", "zetta", "yotta"]
+	},
+	    roundingFuncs = {
+	  floor: Math.floor,
+	  ceil: Math.ceil
 	};
 	/**
 	 * filesize
@@ -57,7 +61,8 @@
 	      separator,
 	      spacer,
 	      standard,
-	      symbols;
+	      symbols,
+	      roundingFunc;
 
 	  if (isNaN(arg)) {
 	    throw new TypeError("Invalid number");
@@ -78,6 +83,7 @@
 	  full = descriptor.fullform === true;
 	  fullforms = descriptor.fullforms instanceof Array ? descriptor.fullforms : [];
 	  e = descriptor.exponent !== void 0 ? descriptor.exponent : -1;
+	  roundingFunc = roundingFuncs[descriptor.roundingMethod] || Math.round;
 	  num = Number(arg);
 	  neg = num < 0;
 	  ceil = base > 2 ? 1000 : 1024; // Flipping a negative number to determine the size
@@ -120,7 +126,8 @@
 	      }
 	    }
 
-	    result[0] = Number(val.toFixed(e > 0 ? round : 0));
+	    var p = Math.pow(10, e > 0 ? round : 0);
+	    result[0] = roundingFunc(val * p) / p;
 
 	    if (result[0] === ceil && e < 8 && descriptor.exponent === void 0) {
 	      result[0] = 1;