转载自: http://demon.tw/programming/javascript-sprintf.html
1 function str_repeat(i, m) { 2 for (var o = []; m > 0; o[--m] = i); 3 return o.join(''); 4 } 5 function sprintf() { 6 var i = 0, a, f = arguments[i++], o = [], m, p, c, x, s = ''; 7 while (f) { 8 if (m = /^[^x25]+/.exec(f)) { 9 o.push(m[0]); 10 } 11 else if (m = /^x25{2}/.exec(f)) { 12 o.push('%'); 13 } 14 else if (m = /^x25(?:(d+)$)?(+)?(0|'[^$])?(-)?(d+)?(?:.(d+))?([b-fosuxX])/.exec(f)) { 15 if (((a = arguments[m[1] || i++]) == null) || (a == undefined)) { 16 throw('Too few arguments.'); 17 } 18 if (/[^s]/.test(m[7]) && (typeof(a) != 'number')) { 19 throw('Expecting number but found ' + typeof(a)); 20 } 21 switch (m[7]) { 22 case 'b': a = a.toString(2); break; 23 case 'c': a = String.fromCharCode(a); break; 24 case 'd': a = parseInt(a); break; 25 case 'e': a = m[6] ? a.toExponential(m[6]) : a.toExponential(); break; 26 case 'f': a = m[6] ? parseFloat(a).toFixed(m[6]) : parseFloat(a); break; 27 case 'o': a = a.toString(8); break; 28 case 's': a = ((a = String(a)) && m[6] ? a.substring(0, m[6]) : a); break; 29 case 'u': a = Math.abs(a); break; 30 case 'x': a = a.toString(16); break; 31 case 'X': a = a.toString(16).toUpperCase(); break; 32 } 33 a = (/[def]/.test(m[7]) && m[2] && a >= 0 ? '+'+ a : a); 34 c = m[3] ? m[3] == '0' ? '0' : m[3].charAt(1) : ' '; 35 x = m[5] - String(a).length - s.length; 36 p = m[5] ? str_repeat(c, x) : ''; 37 o.push(s + (m[4] ? a + p : p + a)); 38 } 39 else { 40 throw('Huh ?!'); 41 } 42 f = f.substring(m[0].length); 43 } 44 return o.join(''); 45 }