javascript sprintf方法

转载自: http://demon.tw/programming/javascript-sprintf.html

 function str_repeat(i, m) {
     for (var o = []; m > 0; o[--m] = i);
     return o.join('');
 }
 function sprintf() {
     var i = 0, a, f = arguments[i++], o = [], m, p, c, x, s = '';
     while (f) {
         if (m = /^[^\x25]+/.exec(f)) {
             o.push(m[0]);
         }
         else if (m = /^\x25{2}/.exec(f)) {
             o.push('%');
         }
         else if (m = /^\x25(?:(\d+)\$)?(\+)?(0|'[^$])?(-)?(\d+)?(?:\.(\d+))?([b-fosuxX])/.exec(f)) {
             if (((a = arguments[m[1] || i++]) == null) || (a == undefined)) {
                 throw('Too few arguments.');
             }
             if (/[^s]/.test(m[7]) && (typeof(a) != 'number')) {
                 throw('Expecting number but found ' + typeof(a));
             }
             switch (m[7]) {
                 case 'b': a = a.toString(2); break;
                 case 'c': a = String.fromCharCode(a); break;
                 case 'd': a = parseInt(a); break;
                 case 'e': a = m[6] ? a.toExponential(m[6]) : a.toExponential(); break;
                 case 'f': a = m[6] ? parseFloat(a).toFixed(m[6]) : parseFloat(a); break;
                 case 'o': a = a.toString(8); break;
                 case 's': a = ((a = String(a)) && m[6] ? a.substring(0, m[6]) : a); break;
                 case 'u': a = Math.abs(a); break;
                 case 'x': a = a.toString(16); break;
                 case 'X': a = a.toString(16).toUpperCase(); break;
             }
             a = (/[def]/.test(m[7]) && m[2] && a >= 0 ? '+'+ a : a);
             c = m[3] ? m[3] == '0' ? '0' : m[3].charAt(1) : ' ';
             x = m[5] - String(a).length - s.length;
             p = m[5] ? str_repeat(c, x) : '';
             o.push(s + (m[4] ? a + p : p + a));
         }
         else {
             throw('Huh ?!');
         }
         f = f.substring(m[0].length);
     }
     return o.join('');
 }