js数字格式化

JS数字格式化函数
关键字: number format
前几天在blog里贴了个JS货币格式化的函数，今天在Matt Snider的网站上淘到了另一个不错的东西，不过和之前说的那个函数有点差别，这个函数是用来格式化数字类型的，很好，很实用。

ps:Matt Snider的网站正如其title一样——Matt Snider JavaScript Resource，内容相当多，个个都比较实用，我喜欢。

/**
* Formats the number according to the ‘format’ string; adherses to the american number standard where a comma is inserted after every 3 digits.
*  note: there should be only 1 contiguous number in the format, where a number consists of digits, period, and commas
*        any other characters can be wrapped around this number, including ‘$’, ‘%’, or text
*        examples (123456.789):
*          ‘0′ - (123456) show only digits, no precision
*          ‘0.00′ - (123456.78) show only digits, 2 precision
*          ‘0.0000′ - (123456.7890) show only digits, 4 precision
*          ‘0,000′ - (123,456) show comma and digits, no precision
*          ‘0,000.00′ - (123,456.78) show comma and digits, 2 precision
*          ‘0,0.00′ - (123,456.78) shortcut method, show comma and digits, 2 precision
*
* @method format
* @param format {string} the way you would like to format this text
* @return {string} the formatted number
* @public
*/

Number.prototype.format = function(format) {
	if (! isType(format, ’string’)) {return ”;} // sanity check

	var hasComma = -1 < format.indexOf(’,'),
		psplit = format.stripNonNumeric().split(’.'),
		that = this;

	// compute precision
	if (1 < psplit.length) {
		// fix number precision
		that = that.toFixed(psplit[1].length);
	}
	// error: too many periods
	else if (2 < psplit.length) {
		throw(’NumberFormatException: invalid format, formats should have no more than 1 period: ‘ + format);
	}
	// remove precision
	else {
		that = that.toFixed(0);
	}

	// get the string now that precision is correct
	var fnum = that.toString();

	// format has comma, then compute commas
	if (hasComma) {
		// remove precision for computation
		psplit = fnum.split(’.');

		var cnum = psplit[0],
			parr = [],
			j = cnum.length,
			m = Math.floor(j / 3),
			n = cnum.length % 3 || 3; // n cannot be ZERO or causes infinite loop

		// break the number into chunks of 3 digits; first chunk may be less than 3
		for (var i = 0; i < j; i += n) {
			if (i != 0) {n = 3;}
			parr[parr.length] = cnum.substr(i, n);
			m -= 1;
		}

		// put chunks back together, separated by comma
		fnum = parr.join(’,');

		// add the precision back in
		if (psplit[1]) {fnum += ‘.’ + psplit[1];}
	}

	// replace the number portion of the format with fnum
	return format.replace(/[d,?.?]+/, fnum);
};