js基礎:Javascript 版本的 Sprintf 字符串格式化函數
[ 來源：js實例 | 作者：js基礎 | 時間：2008-2-22 | 去論壇]
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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);
}

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