JavaScript中数组是无法直接保存为Cookie的（PHP可以），那要将数组转存为字符串，再保存在Cookie中，简单的一维数组我们直接用toString()或者join就可以了：
JavaScript中toString函数方法是返回对象的字符串表示。
使用方法：objectname.toString([radix])
其中objectname是必选项。要得到字符串表示的对象。
radix是可选项。指定将数字值转换为字符串时的进制。
join是其中一个方法。
格式：objArray.join(seperator)
用途：以seperator指定的字符作为分隔符，将数组转换为字符串，当seperator为逗号时，其作用和toString()相同。
如果多维数组，我们就要用JSON了。
JSON(JavaScript Object Notation) 是一种轻量级的数据交换格式。易于人阅读和编写。同时也易于机器解析和生成。它基于JavaScript Programming Language, Standard ECMA-262 3rd Edition - December 1999的一个子集。 JSON采用完全独立于语言的文本格式，但是也使用了类似于C语言家族的习惯（包括C, C++, C#, Java, JavaScript, Perl, Python等）。这些特性使JSON成为理想的数据交换语言。
这里我们使用PHP2JS的函数库来实现，需要 json_decode 和 json_encode这两个函数，懂PHP的朋友可以理解这两个函数的意思。json_decode 是JSON到数组，json_encode 是数组到JSON。
需要注意的是JavaScript 保存 Cookie 会将一些字符过滤，如："{" 被过滤为 "{_" 等。所以在获取 Cookie 时要过滤这些字符，不然 json_decode 会出错。
下面简单举例如下：
复制代码 代码如下:
<script type="text/javascript">
function setCookie(name, value){
    document.cookie = name + "="+ value;
}
function getCookie(name){
    var arr = document.cookie.match(new RegExp("(^| )"+name+"=([^;]*)(;|$)"));
    if(arr != null) return unescape(arr[2]); return '';
}
function savecookie(){
    var dc = {};

    dc['a'] = {};
    dc['a']['x'] = 'ax';
    dc['a']['y'] = 'ay';
    dc['a']['z'] = 'az';

    dc['b'] = {};
    dc['b']['x'] = 'bx';
    dc['b']['y'] = 'by';
    dc['b']['z'] = 'bz';

    var cdc = json_encode(dc);
    setCookie('testcookie', cdc);
}
function clearcookie(){
    setCookie('testcookie', '');
}
function readcookie(){
    var cdc = getCookie('testcookie');
    cdc = cdc.replace(/,_/g, ',');
    cdc = cdc.replace(/{_/g, '{');
    cdc = cdc.replace(/_}/g, '}');
    var dc = json_decode(cdc);
    for(i in dc){
        for(j in dc[i]){
            document.write(i +':'+ j +':'+ dc[i][j] +'<br>');
        }
    }
}
function json_decode(str_json) {
// Decodes the JSON representation into a PHP value
//
// version: 906.1806
// discuss at: http://phpjs.org/functions/json_decode
// + original by: Public Domain (http://www.json.org/json2.js)
// + reimplemented by: Kevin van Zonneveld (http://kevin.vanzonneveld.net)
// + improved by: T.J. Leahy
// * example 1: json_decode('[\n "e",\n {\n "pluribus": "unum"\n}\n]');
// * returns 1: ['e', {pluribus: 'unum'}]
/*
http://www.JSON.org/json2.js
2008-11-19
Public Domain.
NO WARRANTY EXPRESSED OR IMPLIED. USE AT YOUR OWN RISK.
See http://www.JSON.org/js.html
*/
var json = this.window.JSON;
if (typeof json === 'object' && typeof json.parse === 'function') {
return json.parse(str_json);
}
var cx = /[\u0000\u00ad\u0600-\u0604\u070f\u17b4\u17b5\u200c-\u200f\u2028-\u202f\u2060-\u206f\ufeff\ufff0-\uffff]/g;
var j;
var text = str_json;
// Parsing happens in four stages. In the first stage, we replace certain
// Unicode characters with escape sequences. JavaScript handles many characters
// incorrectly, either silently deleting them, or treating them as line endings.
cx.lastIndex = 0;
if (cx.test(text)) {
text = text.replace(cx, function (a) {
return '\\u' +
('0000' + a.charCodeAt(0).toString(16)).slice(-4);
});
}
// In the second stage, we run the text against regular expressions that look
// for non-JSON patterns. We are especially concerned with '()' and 'new'
// because they can cause invocation, and '=' because it can cause mutation.
// But just to be safe, we want to reject all unexpected forms.
// We split the second stage into 4 regexp operations in order to work around
// crippling inefficiencies in IE's and Safari's regexp engines. First we
// replace the JSON backslash pairs with '@' (a non-JSON character). Second, we
// replace all simple value tokens with ']' characters. Third, we delete all
// open brackets that follow a colon or comma or that begin the text. Finally,
// we look to see that the remaining characters are only whitespace or ']' or
// ',' or ':' or '{' or '}'. If that is so, then the text is safe for eval.
if (/^[\],:{}\s]*$/.
test(text.replace(/\\(?:["\\\/bfnrt]|u[0-9a-fA-F]{4})/g, '@').
replace(/"[^"\\\n\r]*"|true|false|null|-?\d+(?:\.\d*)?(?:[eE][+\-]?\d+)?/g, ']').
replace(/(?:^|:|,)(?:\s*\[)+/g, ''))) {
// In the third stage we use the eval function to compile the text into a
// JavaScript structure. The '{' operator is subject to a syntactic ambiguity
// in JavaScript: it can begin a block or an object literal. We wrap the text
// in parens to eliminate the ambiguity.
j = eval('(' + text + ')');
return j;
}
// If the text is not JSON parseable, then a SyntaxError is thrown.
throw new SyntaxError('json_decode');
}
function json_encode(mixed_val) {
// Returns the JSON representation of a value
//
// version: 906.1806
// discuss at: http://phpjs.org/functions/json_encode
// + original by: Public Domain (http://www.json.org/json2.js)
// + reimplemented by: Kevin van Zonneveld (http://kevin.vanzonneveld.net)
// + improved by: T.J. Leahy
// * example 1: json_encode(['e', {pluribus: 'unum'}]);
// * returns 1: '[\n "e",\n {\n "pluribus": "unum"\n}\n]'
/*
http://www.JSON.org/json2.js
2008-11-19
Public Domain.
NO WARRANTY EXPRESSED OR IMPLIED. USE AT YOUR OWN RISK.
See http://www.JSON.org/js.html
*/
var json = this.window.JSON;
if (typeof json === 'object' && typeof json.stringify === 'function') {
return json.stringify(mixed_val);
}
var value = mixed_val;
var quote = function (string) {
var escapable = /[\\\"\u0000-\u001f\u007f-\u009f\u00ad\u0600-\u0604\u070f\u17b4\u17b5\u200c-\u200f\u2028-\u202f\u2060-\u206f\ufeff\ufff0-\uffff]/g;
var meta = { // table of character substitutions
'\b': '\\b',
'\t': '\\t',
'\n': '\\n',
'\f': '\\f',
'\r': '\\r',
'"' : '\\"',
'\\': '\\\\'
};
escapable.lastIndex = 0;
return escapable.test(string) ?
'"' + string.replace(escapable, function (a) {
var c = meta[a];
return typeof c === 'string' ? c :
'\\u' + ('0000' + a.charCodeAt(0).toString(16)).slice(-4);
}) + '"' :
'"' + string + '"';
};
var str = function(key, holder) {
var gap = '';
var indent = ' ';
var i = 0; // The loop counter.
var k = ''; // The member key.
var v = ''; // The member value.
var length = 0;
var mind = gap;
var partial = [];
var value = holder[key];
// If the value has a toJSON method, call it to obtain a replacement value.
if (value && typeof value === 'object' &&
typeof value.toJSON === 'function') {
value = value.toJSON(key);
}
// What happens next depends on the value's type.
switch (typeof value) {
case 'string':
return quote(value);
case 'number':
// JSON numbers must be finite. Encode non-finite numbers as null.
return isFinite(value) ? String(value) : 'null';
case 'boolean':
case 'null':
// If the value is a boolean or null, convert it to a string. Note:
// typeof null does not produce 'null'. The case is included here in
// the remote chance that this gets fixed someday.
return String(value);
case 'object':
// If the type is 'object', we might be dealing with an object or an array or
// null.
// Due to a specification blunder in ECMAScript, typeof null is 'object',
// so watch out for that case.
if (!value) {
return 'null';
}
// Make an array to hold the partial results of stringifying this object value.
gap += indent;
partial = [];
// Is the value an array?
if (Object.prototype.toString.apply(value) === '[object Array]') {
// The value is an array. Stringify every element. Use null as a placeholder
// for non-JSON values.
length = value.length;
for (i = 0; i < length; i += 1) {
partial[i] = str(i, value) || 'null';
}
// Join all of the elements together, separated with commas, and wrap them in
// brackets.
v = partial.length === 0 ? '[]' :
gap ? '[\n' + gap +
partial.join(',\n' + gap) + '\n' +
mind + ']' :
'[' + partial.join(',') + ']';
gap = mind;
return v;
}
// Iterate through all of the keys in the object.
for (k in value) {
if (Object.hasOwnProperty.call(value, k)) {
v = str(k, value);
if (v) {
partial.push(quote(k) + (gap ? ': ' : ':') + v);
}
}
}
// Join all of the member texts together, separated with commas,
// and wrap them in braces.
v = partial.length === 0 ? '{}' :
gap ? '{\n' + gap + partial.join(',\n' + gap) + '\n' +
mind + '}' : '{' + partial.join(',') + '}';
gap = mind;
return v;
}
};
// Make a fake root object containing our value under the key of ''.
// Return the result of stringifying the value.
return str('', {
'': value
});
}
savecookie();
readcookie();
</script>

还要注意的就是中文问题，可能会乱码，建议将多字节字符及中文等用 base64 编码解码：
复制代码 代码如下:
<script type="text/javascript">
function base64_decode( data ) {
// Decodes string using MIME base64 algorithm
//
// version: 905.3122
// discuss at: http://phpjs.org/functions/base64_decode
// + original by: Tyler Akins (http://rumkin.com)
// + improved by: Thunder.m
// + input by: Aman Gupta
// + improved by: Kevin van Zonneveld (http://kevin.vanzonneveld.net)
// + bugfixed by: Onno Marsman
// + bugfixed by: Pellentesque Malesuada
// + improved by: Kevin van Zonneveld (http://kevin.vanzonneveld.net)
// + input by: Brett Zamir (http://brett-zamir.me)
// + bugfixed by: Kevin van Zonneveld (http://kevin.vanzonneveld.net)
// - depends on: utf8_decode
// * example 1: base64_decode('S2V2aW4gdmFuIFpvbm5ldmVsZA==');
// * returns 1: 'Kevin van Zonneveld'
// mozilla has this native
// - but breaks in 2.0.0.12!
//if (typeof this.window['btoa'] == 'function') {
// return btoa(data);
//}
var b64 = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";
var o1, o2, o3, h1, h2, h3, h4, bits, i = 0, ac = 0, dec = "", tmp_arr = [];
if (!data) {
return data;
}
data += '';
do { // unpack four hexets into three octets using index points in b64
h1 = b64.indexOf(data.charAt(i++));
h2 = b64.indexOf(data.charAt(i++));
h3 = b64.indexOf(data.charAt(i++));
h4 = b64.indexOf(data.charAt(i++));
bits = h1<<18 | h2<<12 | h3<<6 | h4;
o1 = bits16 & 0xff;
o2 = bits8 & 0xff;
o3 = bits & 0xff;
if (h3 == 64) {
tmp_arr[ac++] = String.fromCharCode(o1);
} else if (h4 == 64) {
tmp_arr[ac++] = String.fromCharCode(o1, o2);
} else {
tmp_arr[ac++] = String.fromCharCode(o1, o2, o3);
}
} while (i < data.length);
dec = tmp_arr.join('');
dec = this.utf8_decode(dec);
return dec;
}
function base64_encode( data ) {
// Encodes string using MIME base64 algorithm
//
// version: 905.2617
// discuss at: http://phpjs.org/functions/base64_encode
// + original by: Tyler Akins (http://rumkin.com)
// + improved by: Bayron Guevara
// + improved by: Thunder.m
// + improved by: Kevin van Zonneveld (http://kevin.vanzonneveld.net)
// + bugfixed by: Pellentesque Malesuada
// + improved by: Kevin van Zonneveld (http://kevin.vanzonneveld.net)
// - depends on: utf8_encode
// * example 1: base64_encode('Kevin van Zonneveld');
// * returns 1: 'S2V2aW4gdmFuIFpvbm5ldmVsZA=='
// mozilla has this native
// - but breaks in 2.0.0.12!
//if (typeof this.window['atob'] == 'function') {
// return atob(data);
//}
var b64 = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";
var o1, o2, o3, h1, h2, h3, h4, bits, i = 0, ac = 0, enc="", tmp_arr = [];
if (!data) {
return data;
}
data = this.utf8_encode(data+'');
do { // pack three octets into four hexets
o1 = data.charCodeAt(i++);
o2 = data.charCodeAt(i++);
o3 = data.charCodeAt(i++);
bits = o1<<16 | o2<<8 | o3;
h1 = bits18 & 0x3f;
h2 = bits12 & 0x3f;
h3 = bits6 & 0x3f;
h4 = bits & 0x3f;
// use hexets to index into b64, and append result to encoded string
tmp_arr[ac++] = b64.charAt(h1) + b64.charAt(h2) + b64.charAt(h3) + b64.charAt(h4);
} while (i < data.length);
enc = tmp_arr.join('');
switch( data.length % 3 ){
case 1:
enc = enc.slice(0, -2) + '==';
break;
case 2:
enc = enc.slice(0, -1) + '=';
break;
}
return enc;
}
function utf8_encode ( argString ) {
// Encodes an ISO-8859-1 string to UTF-8
//
// version: 905.1217
// discuss at: http://phpjs.org/functions/utf8_encode
// + original by: Webtoolkit.info (http://www.webtoolkit.info/)
// + improved by: Kevin van Zonneveld (http://kevin.vanzonneveld.net)
// + improved by: sowberry
// + tweaked by: Jack
// + bugfixed by: Onno Marsman
// + improved by: Yves Sucaet
// + bugfixed by: Onno Marsman
// * example 1: utf8_encode('Kevin van Zonneveld');
// * returns 1: 'Kevin van Zonneveld'
var string = (argString+'').replace(/\r\n/g, "\n").replace(/\r/g, "\n");
var utftext = "";
var start, end;
var stringl = 0;
start = end = 0;
stringl = string.length;
for (var n = 0; n < stringl; n++) {
var c1 = string.charCodeAt(n);
var enc = null;
if (c1 < 128) {
end++;
} else if((c1 > 127) && (c1 < 2048)) {
enc = String.fromCharCode((c1 6) | 192) + String.fromCharCode((c1 & 63) | 128);
} else {
enc = String.fromCharCode((c1 12) | 224) + String.fromCharCode(((c1 6) & 63) | 128) + String.fromCharCode((c1 & 63) | 128);
}
if (enc !== null) {
if (end > start) {
utftext += string.substring(start, end);
}
utftext += enc;
start = end = n+1;
}
}
if (end > start) {
utftext += string.substring(start, string.length);
}
return utftext;
}
function utf8_decode ( str_data ) {
// Converts a UTF-8 encoded string to ISO-8859-1
//
// version: 905.3122
// discuss at: http://phpjs.org/functions/utf8_decode
// + original by: Webtoolkit.info (http://www.webtoolkit.info/)
// + input by: Aman Gupta
// + improved by: Kevin van Zonneveld (http://kevin.vanzonneveld.net)
// + improved by: Norman "zEh" Fuchs
// + bugfixed by: hitwork
// + bugfixed by: Onno Marsman
// + input by: Brett Zamir (http://brett-zamir.me)
// + bugfixed by: Kevin van Zonneveld (http://kevin.vanzonneveld.net)
// * example 1: utf8_decode('Kevin van Zonneveld');
// * returns 1: 'Kevin van Zonneveld'
var tmp_arr = [], i = 0, ac = 0, c1 = 0, c2 = 0, c3 = 0;
str_data += '';
while ( i < str_data.length ) {
c1 = str_data.charCodeAt(i);
if (c1 < 128) {
tmp_arr[ac++] = String.fromCharCode(c1);
i++;
} else if ((c1 > 191) && (c1 < 224)) {
c2 = str_data.charCodeAt(i+1);
tmp_arr[ac++] = String.fromCharCode(((c1 & 31) << 6) | (c2 & 63));
i += 2;
} else {
c2 = str_data.charCodeAt(i+1);
c3 = str_data.charCodeAt(i+2);
tmp_arr[ac++] = String.fromCharCode(((c1 & 15) << 12) | ((c2 & 63) << 6) | (c3 & 63));
i += 3;
}
}
return tmp_arr.join('');
}
</script>

base64_decode 依赖 utf8_decode ，base64_encode 依赖 utf8_encode。

PHP2JS是开源项目，是将PHP的部分函数实现到JavaScript。