js基础:Javascript 版本的 Sprintf 字符串格式化函数
[ 来源：js实例 | 作者：js基础 | 时间：2008-2-22 | 去论坛]
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/*** sprintf.js -- POSIX sprintf(3) style formatting function for JavaScript** Copyright (c) 2006-2007 Ralf S. Engelschall <rse@engelschall.com>** Partly based on Public Domain code by Jan Moesen <http://jan.moesen.nu/>** Licensed under GPL <http://www.gnu.org/licenses/gpl.txt>**** $LastChangedDate$** $LastChangedRevision$*//* make sure the ECMAScript 3.0 Number.toFixed() method is available */if (typeof Number.prototype.toFixed != "undefined") { (function(){ /* see http://www.jibbering.com/faq/#FAQ4_6 for details */ function Stretch(Q, L, c) { var S = Q if (c.length > 0) while (S.length < L) S = c+S; return S; } function StrU(X, M, N) { /* X >= 0.0 */ var T, S; S = new String(Math.round(X * Number("1e"+N))); if (S.search && S.search(/\D/) != -1) return ''+X; with (new String(Stretch(S, M+N, '0'))) return substring(0, T=(length-N)) + '.' + substring(T); } function Sign(X) { return X < 0 ? '-' : ''; } function StrS(X, M, N) { return Sign(X)+StrU(Math.abs(X), M, N); } Number.prototype.toFixed = function (n) { return StrS(this, 1, n) }; })();}/* the sprintf() function */sprintf = function () { /* argument sanity checking */ if (!arguments || arguments.length < 1) alert("sprintf:ERROR: not enough arguments"); /* initialize processing queue */ var argumentnum = 0; var done = "", todo = arguments[argumentnum++]; /* parse still to be done format string */ var m; while (m = /^([^%]*)%(\d+$)?([#0 +'-]+)?(\*|\d+)?(\.\*|\.\d+)?([%diouxXfFcs])(.*)$/.exec(todo)) { var pProlog = m[1], pAccess = m[2], pFlags = m[3], pMinLength = m[4], pPrecision = m[5], pType = m[6], pEpilog = m[7]; /* determine substitution */ var subst; if (pType == '%') /* special case: escaped percent character */ subst = '%'; else { /* parse padding and justify aspects of flags */ var padWith = ' '; var justifyRight = true; if (pFlags) { if (pFlags.indexOf('0') >= 0) padWith = '0'; if (pFlags.indexOf('-') >= 0) { padWith = ' '; justifyRight = false; } } else pFlags = ""; /* determine minimum length */ var minLength = -1; if (pMinLength) { if (pMinLength == "*") { var access = argumentnum++; if (access >= arguments.length) alert("sprintf:ERROR: not enough arguments"); minLength = arguments[access]; } else minLength = parseInt(pMinLength, 10); } /* determine precision */ var precision = -1; if (pPrecision) { if (pPrecision == ".*") { var access = argumentnum++; if (access >= arguments.length) alert("sprintf:ERROR: not enough arguments"); precision = arguments[access]; } else precision = parseInt(pPrecision.substring(1), 10); } /* determine how to fetch argument */ var access = argumentnum++; if (pAccess) access = parseInt(pAccess.substring(0, pAccess.length - 1), 10); if (access >= arguments.length) alert("sprintf:ERROR: not enough arguments"); /* dispatch into expansions according to type */ var prefix = ""; switch (pType) { case 'd': case 'i': subst = arguments[access]; if (typeof subst != "number") subst = 0; subst = subst.toString(10); if (pFlags.indexOf('#') >= 0 && subst >= 0) subst = "+" + subst; if (pFlags.indexOf(' ') >= 0 && subst >= 0) subst = " " + subst; break; case 'o': subst = arguments[access]; if (typeof subst != "number") subst = 0; subst = subst.toString(8); break; case 'u': subst = arguments[access]; if (typeof subst != "number") subst = 0; subst = Math.abs(subst); subst = subst.toString(10); break;
case 'x':
subst = arguments[access];
if (typeof subst != "number")
subst = 0;
subst = subst.toString(16).toLowerCase();
if (pFlags.indexOf('#') >= 0)
prefix = "0x";
break;
case 'X':
subst = arguments[access];
if (typeof subst != "number")
subst = 0;
subst = subst.toString(16).toUpperCase();
if (pFlags.indexOf('#') >= 0)
prefix = "0X";
break;
case 'f':
case 'F':
subst = arguments[access];
if (typeof subst != "number")
subst = 0.0;
subst = 0.0 + subst;
if (precision > -1) {
if (subst.toFixed)
subst = subst.toFixed(precision);
else {
subst = (Math.round(subst * Math.pow(10, precision)) / Math.pow(10, precision));
subst += "0000000000";
subst = subst.substr(0, subst.indexOf(".")+precision+1);
}
}
subst = '' + subst;
if (pFlags.indexOf("'") >= 0) {
var k = 0;
for (var i = (subst.length - 1) - 3; i >= 0; i -= 3) {
subst = subst.substring(0, i) + (k == 0 ? "." : ",") + subst.substring(i);
k = (k + 1) % 2;
}
}
break;
case 'c':
subst = arguments[access];
if (typeof subst != "number")
subst = 0;
subst = String.fromCharCode(subst);
break;
case 's':
subst = arguments[access];
if (precision > -1)
subst = subst.substr(0, precision);
if (typeof subst != "string")
subst = "";
break;
}
/* apply optional padding */
var padding = minLength - subst.toString().length - prefix.toString().length;
if (padding > 0) {
var arrTmp = new Array(padding + 1);
if (justifyRight)
subst = arrTmp.join(padWith) + subst;
else
subst = subst + arrTmp.join(padWith);
}
/* add optional prefix */
subst = prefix + subst;
}
/* update the processing queue */
done = done + pProlog + subst;
todo = pEpilog;
}
return (done + todo);
}