Javascript sprintf

Several programming languages implement a sprintf function, to output a formatted string. It originated from the C programming language, printf function. Its a string manipulation function.

This is limited sprintf Javascript implementation. Function returns a string formatted by the usual printf conventions. See below for more details. You must specify the string and how to format the variables in it. Possible format values:

%% – Returns a percent sign
%b – Binary number
%c – The character according to the ASCII value
%d – Signed decimal number
%f – Floating-point number
%o – Octal number
%s – String
%x – Hexadecimal number (lowercase letters)
%X – Hexadecimal number (uppercase letters)

Additional format values. These are placed between the % and the letter (example %.2f):

+ (Forces both + and – in front of numbers. By default, only negative numbers are marked)
– (Left-justifies the variable value)
0 zero will be used for padding the results to the right string size
[0-9] (Specifies the minimum width held of to the variable value)
.[0-9] (Specifies the number of decimal digits or maximum string length)

If you plan using UTF-8 encoding in your project don’t forget to set the page encoding to UTF-8 (Content-Type meta tag), and use Javascript UTF-8 utility found on this website.

DEMO

Source code for webtoolkit.sprintf.js

/**
*
*  Javascript sprintf
*  http://www.webtoolkit.info/
*
*
**/
 
sprintfWrapper = {
 
	init : function () {
 
		if (typeof arguments == "undefined") { return null; }
		if (arguments.length &lt; 1) { return null; }
		if (typeof arguments[0] != "string") { return null; }
		if (typeof RegExp == "undefined") { return null; }
 
		var string = arguments[0];
		var exp = new RegExp(/(%([%]|(\-)?(\+|\x20)?(0)?(\d+)?(\.(\d)?)?([bcdfosxX])))/g);
		var matches = new Array();
		var strings = new Array();
		var convCount = 0;
		var stringPosStart = 0;
		var stringPosEnd = 0;
		var matchPosEnd = 0;
		var newString = '';
		var match = null;
 
		while (match = exp.exec(string)) {
			if (match[9]) { convCount += 1; }
 
			stringPosStart = matchPosEnd;
			stringPosEnd = exp.lastIndex - match[0].length;
			strings[strings.length] = string.substring(stringPosStart, stringPosEnd);
 
			matchPosEnd = exp.lastIndex;
			matches[matches.length] = {
				match: match[0],
				left: match[3] ? true : false,
				sign: match[4] || '',
				pad: match[5] || ' ',
				min: match[6] || 0,
				precision: match[8],
				code: match[9] || '%',
				negative: parseInt(arguments[convCount]) &lt; 0 ? true : false,
				argument: String(arguments[convCount])
			};
		}
		strings[strings.length] = string.substring(matchPosEnd);
 
		if (matches.length == 0) { return string; }
		if ((arguments.length - 1) &lt; convCount) { return null; }
 
		var code = null;
		var match = null;
		var i = null;
 
		for (i=0; i&lt;matches.length; i++) {
 
			if (matches[i].code == '%') { substitution = '%' }
			else if (matches[i].code == 'b') {
				matches[i].argument = String(Math.abs(parseInt(matches[i].argument)).toString(2));
				substitution = sprintfWrapper.convert(matches[i], true);
			}
			else if (matches[i].code == 'c') {
				matches[i].argument = String(String.fromCharCode(parseInt(Math.abs(parseInt(matches[i].argument)))));
				substitution = sprintfWrapper.convert(matches[i], true);
			}
			else if (matches[i].code == 'd') {
				matches[i].argument = String(Math.abs(parseInt(matches[i].argument)));
				substitution = sprintfWrapper.convert(matches[i]);
			}
			else if (matches[i].code == 'f') {
				matches[i].argument = String(Math.abs(parseFloat(matches[i].argument)).toFixed(matches[i].precision ? matches[i].precision : 6));
				substitution = sprintfWrapper.convert(matches[i]);
			}
			else if (matches[i].code == 'o') {
				matches[i].argument = String(Math.abs(parseInt(matches[i].argument)).toString(8));
				substitution = sprintfWrapper.convert(matches[i]);
			}
			else if (matches[i].code == 's') {
				matches[i].argument = matches[i].argument.substring(0, matches[i].precision ? matches[i].precision : matches[i].argument.length)
				substitution = sprintfWrapper.convert(matches[i], true);
			}
			else if (matches[i].code == 'x') {
				matches[i].argument = String(Math.abs(parseInt(matches[i].argument)).toString(16));
				substitution = sprintfWrapper.convert(matches[i]);
			}
			else if (matches[i].code == 'X') {
				matches[i].argument = String(Math.abs(parseInt(matches[i].argument)).toString(16));
				substitution = sprintfWrapper.convert(matches[i]).toUpperCase();
			}
			else {
				substitution = matches[i].match;
			}
 
			newString += strings[i];
			newString += substitution;
 
		}
		newString += strings[i];
 
		return newString;
 
	},
 
	convert : function(match, nosign){
		if (nosign) {
			match.sign = '';
		} else {
			match.sign = match.negative ? '-' : match.sign;
		}
		var l = match.min - match.argument.length + 1 - match.sign.length;
		var pad = new Array(l &lt; 0 ? 0 : l).join(match.pad);
		if (!match.left) {
			if (match.pad == "0" || nosign) {
				return match.sign + pad + match.argument;
			} else {
				return pad + match.sign + match.argument;
			}
		} else {
			if (match.pad == "0" || nosign) {
				return match.sign + match.argument + pad.replace(/0/g, ' ');
			} else {
				return match.sign + match.argument + pad;
			}
		}
	}
}
 
sprintf = sprintfWrapper.init;