{"id":1049,"date":"2012-05-16T16:54:05","date_gmt":"2012-05-16T22:54:05","guid":{"rendered":"http:\/\/bateru.com\/news\/?p=1049"},"modified":"2012-05-21T16:04:56","modified_gmt":"2012-05-21T22:04:56","slug":"code-of-the-day-javascript-decimal-expansion-a-k-a-division","status":"publish","type":"post","link":"https:\/\/bateru.com\/news\/2012\/05\/code-of-the-day-javascript-decimal-expansion-a-k-a-division\/","title":{"rendered":"Code of the Day: Javascript Decimal Expansion a.k.a Division"},"content":{"rendered":"

<\/a>
\nToday’s Code of the Day is about decimal expansion, which is just division. <\/p>\n

So you might be asking yourself, “if decimal expansion is divsion. Then why not use a\/b?”.
\nWell the problem is that Javascript has a ton of problems when dealing with floating point operations because of the way they are stored.<\/p>\n

Examples:<\/b>
\n<\/p>\n

\r\nvar a = 1\/3;\r\na.toString()     \/\/ returns  \"0.3333333333333333\"\r\na.toFixed(25);   \/\/ returns \"0.3333333333333333148296163\"\r\n0.1 + 0.2;       \/\/ returns 0.30000000000000004\r\n<\/pre>\n
<\/code><\/p>\n
Source for decimalExpansion()<\/b>
\n<\/p>\n
\r\n\/\/ borrowed from jQuery 1.7.2\r\nvar isNumeric = function(val){\r\n\treturn !isNaN(parseFloat(val)) && isFinite(val);\r\n};\r\n\/**\r\n* @author Larry Battle \r\n* @date May 16, 2012\r\n* @license MIT and GPLv3\r\n*\/\r\n\/\/decimalExpansion returns a string representation of a divided by b to a fixed length.\r\n\/\/ All the paramaters must be whole numbers.\r\n\/\/ Example: decimalExpansion( 1, 3, 3 ) === \"0.333\"\r\nvar decimalExpansion = function (top, bottom, decLength) {\r\n\tif (!isNumeric(top) || !isNumeric(bottom) || !isNumeric(decLength) || !bottom) {\r\n\t\treturn null;\r\n\t}\r\n\tvar sign = ((top * bottom) != Math.abs(top * bottom)) ? \"-\" : \"\";\r\n\ttop = Math.abs(top);\r\n\tbottom = Math.abs(bottom);\r\n\tdecLength = Math.abs(decLength);\r\n\t\r\n\tvar result = Math.floor(top \/ bottom),\r\n\tremainder = top % bottom,\r\n\tmaxDecimal = 100,\r\n\ti = Math.min(Math.max(0, decLength), maxDecimal) + 1;\r\n\t\r\n\tif (1 < i) {\r\n\t\tresult += \".\";\r\n\t\twhile (i--) {\r\n\t\t\ttop = remainder * 10;\r\n\t\t\tremainder = top % bottom;\r\n\t\t\tresult += \"\" + Math.floor(top \/ bottom);\r\n\t\t}\r\n\t\tresult = result.replace(\/(\\d)(\\d)$\/, function (match, a, b) {\r\n\t\t\t\treturn +b > 4 ? +a + 1 : a;\r\n\t\t\t});\r\n\t}\r\n\treturn sign + result;\r\n};\r\n<\/pre>\n
<\/code><\/p>\n
Test cases:<\/b>
\n