sprintf.js

function sprintf() {
        if (!arguments || arguments.length < 1 || !RegExp) { return; }
        var str = arguments[0];
        var re = /([^%]*)%('.|0|\x20)?(-)?(\d+)?(\.\d+)?(%|b|c|d|u|f|o|s|x|X)(.*)/;
        var b = [], numSubstitutions = 0, numMatches = 0;
        while (1) {
            var a = re.exec(str);
            if (!a) { break; }
            var leftpart = a[1], pPad = a[2], pJustify = a[3], pMinLength = a[4];
            var pPrecision = a[5], pType = a[6], rightPart = a[7];
            numMatches++;
            if (pType == '%') { subst = '%'; } else {
                numSubstitutions++;
                if (numSubstitutions >= arguments.length) { break; }
                var param = arguments[numSubstitutions];
                var pad = '';
                    if (pPad && pPad.substr(0,1) == "'") pad = leftpart.substr(1,1);
                else if (pPad) pad = pPad;
                var justifyRight = true;
                    if (pJustify && pJustify === "-") justifyRight = false;
                var minLength = -1;
                    if (pMinLength) minLength = parseInt(pMinLength);
                var precision = -1;
                    if (pPrecision && pType == 'f') precision = parseInt(pPrecision.substring(1));
                var subst = param;
                    if (pType == 'b') subst = parseInt(param).toString(2);
                else if (pType == 'c') subst = String.fromCharCode(parseInt(param));
                else if (pType == 'd') subst = parseInt(param) ? parseInt(param) : 0;
                else if (pType == 'u') subst = Math.abs(param);
                else if (pType == 'f') subst = (precision > -1) ? Math.round(parseFloat(param) * Math.pow(10, precision)) / Math.pow
(10, precision): parseFloat(param);
                else if (pType == 'o') subst = parseInt(param).toString(8);
                else if (pType == 's') subst = param;
                else if (pType == 'x') subst = ('' + parseInt(param).toString(16)).toLowerCase();
                else if (pType == 'X') subst = ('' + parseInt(param).toString(16)).toUpperCase();
            }
            str = leftpart + subst + rightPart;
        }
        return str;
}