JavaScript中实现sprintf、printf函数

sprintfWrapper = {

  init : function () {

    if (typeof arguments == "undefined") { return null; }
    if (arguments.length < 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]) < 0 ? true : false,
        argument: String(arguments[convCount])
      };
    }
    strings[strings.length] = string.substring(matchPosEnd);

    if (matches.length == 0) { return string; }
    if ((arguments.length - 1) < convCount) { return null; }

    var code = null;
    var match = null;
    var i = null;

    for (i=0; i<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 < 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;