Refactored to ES6, with transpiling to ES5

Reformatting `else` statements

Gruntfile.js

@@ -22,7 +22,7 @@ module.exports = function(grunt) {
 					"src/si.js",
 					"src/outro.js"
 				],
-				dest : "lib/filesize.js"
+				dest : "lib/filesize.es6.js"
 			}
 		},
 		exec : {
@@ -33,11 +33,15 @@ module.exports = function(grunt) {
 				cmd : "echo //@ sourceMappingURL=<%= pkg.name %>.map >> lib/<%= pkg.name %>.min.js"
 			}
 		},
-		jshint : {
-			options : {
-				jshintrc : ".jshintrc"
+		"6to5": {
+			options: {
+				sourceMap: false
 			},
-			src : "lib/<%= pkg.name %>.js"
+			dist: {
+				files: {
+					"lib/<%= pkg.name %>.js": "lib/<%= pkg.name %>.es6.js"
+				}
+			}
 		},
 		nodeunit : {
 			all : ["test/*.js"]
@@ -80,12 +84,12 @@ module.exports = function(grunt) {
 	grunt.loadNpmTasks("grunt-sed");
 	grunt.loadNpmTasks("grunt-contrib-concat");
 	grunt.loadNpmTasks("grunt-contrib-nodeunit");
-	grunt.loadNpmTasks("grunt-contrib-jshint");
 	grunt.loadNpmTasks('grunt-contrib-watch');
 	grunt.loadNpmTasks("grunt-contrib-uglify");
+	grunt.loadNpmTasks("grunt-6to5");
 
 	// aliases
-	grunt.registerTask("test", ["jshint", "nodeunit"]);
-	grunt.registerTask("build", ["concat", "sed"]);
+	grunt.registerTask("test", [ "nodeunit"]);
+	grunt.registerTask("build", ["concat", "sed", "6to5"]);
 	grunt.registerTask("default", ["build", "test", "uglify"]);
 };

lib/filesize.es6.js

@@ -0,0 +1,145 @@
+/**
+ * filesize
+ *
+ * @author Jason Mulligan <jason.mulligan@avoidwork.com>
+ * @copyright 2015 Jason Mulligan
+ * @license BSD-3 <https://raw.github.com/avoidwork/filesize.js/master/LICENSE>
+ * @link http://filesizejs.com
+ * @module filesize
+ * @version 3.1.0
+ */
+( global ) => {
+const bit = /b$/;
+
+/**
+ * filesize
+ *
+ * @method filesize
+ * @param  {Mixed}   arg        String, Int or Float to transform
+ * @param  {Object}  descriptor [Optional] Flags
+ * @return {String}             Readable file size String
+ */
+let filesize = ( arg, descriptor ) => {
+	let result = [],
+		skip = false,
+		val = 0,
+		e, base, bits, ceil, neg, num, output, round, unix, spacer, suffixes;
+
+	if ( isNaN( arg ) ) {
+		throw new Error( "Invalid arguments" );
+	}
+
+	descriptor = descriptor || {};
+	bits = ( descriptor.bits === true );
+	unix = ( descriptor.unix === true );
+	base = descriptor.base !== undefined ? descriptor.base : 2;
+	round = descriptor.round !== undefined ? descriptor.round : unix ? 1 : 2;
+	spacer = descriptor.spacer !== undefined ? descriptor.spacer : unix ? "" : " ";
+	suffixes = descriptor.suffixes !== undefined ? descriptor.suffixes : {};
+	output = descriptor.output !== undefined ? descriptor.output : "string";
+	e = descriptor.exponent !== undefined ? descriptor.exponent : -1;
+	num = Number( arg );
+	neg = ( num < 0 );
+	ceil = base > 2 ? 1000 : 1024;
+
+	// Flipping a negative number to determine the size
+	if ( neg ) {
+		num = -num;
+	}
+
+	// Zero is now a special case because bytes divide by 1
+	if ( num === 0 ) {
+		result[ 0 ] = 0;
+
+		if ( unix ) {
+			result[ 1 ] = "";
+		} else {
+			result[ 1 ] = "B";
+		}
+	} else {
+		// Determining the exponent
+		if ( e === -1 || isNaN( e ) ) {
+			e = Math.floor( Math.log( num ) / Math.log( ceil ) );
+		}
+
+		// Exceeding supported length, time to reduce & multiply
+		if ( e > 8 ) {
+			val = val * ( 1000 * ( e - 8 ) );
+			e = 8;
+		}
+
+		if ( base === 2 ) {
+			val = num / Math.pow( 2, ( e * 10 ) );
+		} else {
+			val = num / Math.pow( 1000, e );
+		}
+
+		if ( bits ) {
+			val = ( val * 8 );
+
+			if ( val > ceil ) {
+				val = val / ceil;
+				e++;
+			}
+		}
+
+		result[ 0 ] = Number( val.toFixed( e > 0 ? round : 0 ) );
+		result[ 1 ] = si[ bits ? "bits" : "bytes" ][ e ];
+
+		if ( !skip && unix ) {
+			if ( bits && bit.test( result[ 1 ] ) ) {
+				result[ 1 ] = result[ 1 ].toLowerCase();
+			}
+
+			result[ 1 ] = result[ 1 ].charAt( 0 );
+
+			if ( result[ 1 ] === "B" ) {
+				result[ 0 ] = Math.floor( result[ 0 ] );
+				result[ 1 ] = "";
+			} else if ( !bits && result[ 1 ] === "k" ) {
+				result[ 1 ] = "K";
+			}
+		}
+	}
+
+	// Decorating a 'diff'
+	if ( neg ) {
+		result[ 0 ] = -result[ 0 ];
+	}
+
+	// Applying custom suffix
+	result[ 1 ] = suffixes[ result[ 1 ] ] || result[ 1 ];
+
+	// Returning Array, Object, or String (default)
+	if ( output === "array" ) {
+		return result;
+	} else if ( output === "exponent" ) {
+		return e;
+	} else if ( output === "object" ) {
+		return { value: result[ 0 ], suffix: result[ 1 ] };
+	} else {
+		return result.join( spacer );
+	}
+}
+
+/**
+ * SI suffixes
+ *
+ * @type {Object}
+ */
+const si = {
+	bits: [ "B", "kb", "Mb", "Gb", "Tb", "Pb", "Eb", "Zb", "Yb" ],
+	bytes: [ "B", "kB", "MB", "GB", "TB", "PB", "EB", "ZB", "YB" ]
+};
+
+// CommonJS, AMD, script tag
+if ( typeof exports !== "undefined" ) {
+	module.exports = filesize;
+} else if ( typeof define === "function" ) {
+	define( () => {
+		return filesize;
+	} );
+} else {
+	global.filesize = filesize;
+}
+}( this );