* 字符编码

** 一定要知道数据的字符编码

** 使用utf-8字符编码存储数据

** 使用utf-8字符编码输出数据

* Crypto.js 支持中文

Base64编码说明

Base64编码要求把3个8位字节（3*8=24）转化为4个6位的字节（4*6=24），之后在6位的前面补两个0，形成8位一个字节的形式。

如果剩下的字符不足3个字节，则用0填充，输出字符使用'='，因此编码后输出的文本末尾可能会出现1或2个'='。

为了保证所输出的编码位可读字符，Base64制定了一个编码表，以便进行统一转换。编码表的大小为2^6=64，这也是Base64名称的由来。

* 运算符优先级

* /

%

+ -

<< >>

==  ===

|  &

||   &&

// http://tool.oschina.net/encrypt?type=3

var CryptoJS = CryptoJS || function(h, o) {
var f = {};
var j = f.lib = {};
var k = j.Base = function() {
function a() {}
return {
extend: function(b) {
a.prototype = this;
var c = new a;
b && c.mixIn(b);
c.$super = this;
return c
},
create: function() {
var a = this.extend();
a.init.apply(a, arguments);
return a
},
init: function() {},
mixIn: function(a) {
for (var c in a)
a.hasOwnProperty(c) && (this[c] = a[c]);
a.hasOwnProperty("toString") && (this.toString = a.toString)
},
clone: function() {
return this.$super.extend(this)
}
}
}();
var i = j.WordArray = k.extend({
init: function(a, b) {
a = this.words = a || [];
this.sigBytes = b != o ? b : 4 * a.length
},
toString: function(a) {
return (a || p).stringify(this)
},
concat: function(a) {
var b = this.words
, c = a.words
, d = this.sigBytes
, a = a.sigBytes;
this.clamp();
if (d % 4)
for (var e = 0; e < a; e++) b[d + e >>> 2] |= (c[e >>> 2]
>>> 24 - 8 * (e % 4) & 255)
<< 24 - 8 * ((d + e) % 4); else if (65535 < c.length) for (e = 0; e < a; e += 4) b[d + e >>> 2] = c[e >>> 2];
else
b.push.apply(b, c);
this.sigBytes += a;
return this
},
clamp: function() {
var a = this.words
, b = this.sigBytes;
a[b >>> 2] &= 4294967295 << 32 - 8 * (b % 4); a.length = h.ceil(b / 4) }, clone: function() { var a = k.clone.call(this); a.words = this.words.slice(0); return a }, random: function(a) { for (var b = [], c = 0; c < a; c += 4) b.push(4294967296 * h.random() | 0); return i.create(b, a) } }), l = f.enc = {}, p = l.Hex = { stringify: function(a) { for (var b = a.words, a = a.sigBytes, c = [], d = 0; d < a; d++) { var e = b[d >>> 2] >>> 24 - 8 * (d % 4) & 255;
c.push((e >>> 4).toString(16));
c.push((e & 15).toString(16))
}
return c.join("")
},
parse: function(a) {
for (var b = a.length, c = [], d = 0; d < b; d += 2) c[d >>> 3] |= parseInt(a.substr(d, 2), 16) << 24 - 4 * (d % 8); return i.create(c, b / 2) } }, n = l.Latin1 = { stringify: function(a) { for (var b = a.words, a = a.sigBytes, c = [], d = 0; d < a; d++) c.push(String.fromCharCode(b[d >>> 2] >>> 24 - 8 * (d % 4) & 255));
return c.join("")
},
parse: function(a) {
for (var b = a.length, c = [], d = 0; d < b; d++) c[d >>> 2] |= (a.charCodeAt(d) & 255) << 24 - 8 * (d % 4);
return i.create(c, b)
}
}, q = l.Utf8 = {
stringify: function(a) {
try {
return decodeURIComponent(escape(n.stringify(a)))
} catch (b) {
throw Error("Malformed UTF-8 data");
}
},
parse: function(a) {
return n.parse(unescape(encodeURIComponent(a)))
}
}, m = j.BufferedBlockAlgorithm = k.extend({
reset: function() {
this._data = i.create();
this._nDataBytes = 0
},
_append: function(a) {
"string" == typeof a && (a = q.parse(a));
this._data.concat(a);
this._nDataBytes += a.sigBytes
},
_process: function(a) {
var b = this._data
, c = b.words
, d = b.sigBytes
, e = this.blockSize
, f = d / (4 * e)
, f = a ? h.ceil(f) : h.max((f | 0) - this._minBufferSize, 0)
, a = f * e
, d = h.min(4 * a, d);
if (a) {
for (var g = 0; g < a; g += e)
this._doProcessBlock(c, g);
g = c.splice(0, a);
b.sigBytes -= d
}
return i.create(g, d)
},
clone: function() {
var a = k.clone.call(this);
a._data = this._data.clone();
return a
},
_minBufferSize: 0
});
j.Hasher = m.extend({
init: function() {
this.reset()
},
reset: function() {
m.reset.call(this);
this._doReset()
},
update: function(a) {
this._append(a);
this._process();
return this
},
finalize: function(a) {
a && this._append(a);
this._doFinalize();
return this._hash
},
clone: function() {
var a = m.clone.call(this);
a._hash = this._hash.clone();
return a
},
blockSize: 16,
_createHelper: function(a) {
return function(b, c) {
return a.create(c).finalize(b)
}
},
_createHmacHelper: function(a) {
return function(b, c) {
return r.HMAC.create(a, c).finalize(b)
}
}
});
var r = f.algo = {};
return f
}(Math);

(function() {
var h = CryptoJS
, i = h.lib.WordArray;
h.enc.Base64 = {
stringify: function(b) {
var e = b.words
, f = b.sigBytes
, c = this._map;
b.clamp();
for (var b = [], a = 0; a < f; a += 3) for (var d = (e[a >>> 2] >>> 24 - 8 * (a % 4) & 255) << 16 | (e[a + 1 >>> 2] >>> 24 - 8 * ((a + 1) % 4) & 255) << 8 | e[a + 2 >>> 2] >>> 24 - 8 * ((a + 2) % 4) & 255,
g = 0;
4 > g && a + 0.75 * g < f; g++) b.push(c.charAt(d >>> 6 * (3 - g) & 63));
if (e = c.charAt(64))
for (; b.length % 4; )
b.push(e);
return b.join("")
},
parse: function(b) {
var b = b.replace(/\s/g, "")
, e = b.length
, f = this._map
, c = f.charAt(64);
c && (c = b.indexOf(c),
-1 != c && (e = c));
for (var c = [], a = 0, d = 0; d < e; d++) if (d % 4) { var g = f.indexOf(b.charAt(d - 1)) << 2 * (d % 4) , h = f.indexOf(b.charAt(d)) >>> 6 - 2 * (d % 4);
c[a >>> 2] |= (g | h) << 24 - 8 * (a % 4);
a++
}
return i.create(c, a)
},
_map: "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/="
}
}
)();

　　test:

var str=CryptoJS.enc.Utf8.parse("这是一个测试用例");
var base64=CryptoJS.enc.Base64.stringify(str);

console.log(base64);

var words = CryptoJS.enc.Base64.parse(base64);
console.log(words.toString(CryptoJS.enc.Utf8));

* 仅支持ascii版本

https://blog.csdn.net/chenxiaohua/article/details/4084602

(function() {
var g_pCodes = (function() {
var s = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz01234567890+/="
var a = new Array(s.length);
for (var i = 0, n = a.length; i < n; i++) {
a[i] = s.charCodeAt(i);
}
return a;
})();

// 256  
var g\_pMap = \[  
255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,  
255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,  
255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,  
255, 255, 255, 255, 255, 255, 255,  62, 255, 255, 255,  63,  
52,  53,  54,  55,  56,  57,  58,  59,  60,  61, 255, 255,  
255, 254, 255, 255, 255,   0,   1,   2,   3,   4,   5,   6,  
7,   8,   9,  10,  11,  12,  13,  14,  15,  16,  17,  18,  
19,  20,  21,  22,  23,  24,  25, 255, 255, 255, 255, 255,  
255,  26,  27,  28,  29,  30,  31,  32,  33,  34,  35,  36,  
37,  38,  39,  40,  41,  42,  43,  44,  45,  46,  47,  48,  
49,  50,  51, 255, 255, 255, 255, 255, 255, 255, 255, 255,  
255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,  
255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,  
255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,  
255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,  
255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,  
255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,  
255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,  
255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,  
255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,  
255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,  
255, 255, 255, 255  
\];

var encode = function(s) {  
var pIn = s.split('').map(function(c) {  
    return c.charCodeAt(0);  
});

var uInLen = s.length;  
var pIndex = 0;  
var len2 = Math.floor((uInLen+2)/3)<<2;  
var pOut = \[\], p = 0;  
var a, b, c;

for (var i = 0, len = 3 \* Math.floor(uInLen/3); i < len; i+=3) {  
    a = pIn\[i\], b = pIn\[i+1\], c = pIn\[i+2\];  
    pOut.push( g\_pCodes\[ a >> 2 \] );  
    pOut.push( g\_pCodes\[((a & 3) << 4) + (b>>4)\] );  
    pOut.push( g\_pCodes\[((b & 0xf) << 2) + (c>>6)\] );  
    pOut.push( g\_pCodes\[ c & 0x3f\]);  
}

a = pIn\[i\], b = (i+1)<uInLen ? pIn\[i+1\]:0, c = 0;  
if (i < uInLen) {  
    pOut.push( g\_pCodes\[a>>2\]);  
    pOut.push( g\_pCodes\[ ((a & 3)<<4) + (b >> 4)\] );  
    pOut.push( ((i+1)<uInLen) ?  
           g\_pCodes\[((b & 0xf) << 2)+(c>>6)\] :  
           '='.charCodeAt(0));  
    pOut.push( '='.charCodeAt(0) );  
}

return pOut.map(function(c) {  
    return String.fromCharCode(c);  
}).join('');  
};

var decode = function(s) {  
var x, y, z, t, c, g = 3;  
var strIn = s.split('').map(function(c) {  
    return c.charCodeAt(0);  
});  
var out = \[\];

for (x = y = z = t = 0; x < strIn.length; x++) {  
    c = g\_pMap\[strIn\[x\]\];  
    if (c===255) {continue; }  
    if (c===254) {c = 0, g--;}

    t = (t << 6) | c;

    if (++y === 4) {  
    out.push( (t >> 16) & 255 ), z++;  
    if (g > 1) {  
        out.push((t >> 8) & 255), z++;  
    }  
    if (g > 2) {  
        out.push(t & 255), z++;  
    }  
    y = t = 0;  
    }  
}  
return out.map(function(c) {  
    return String.fromCharCode(c);  
}).join('');  
};

return base64 = {  
encode: encode,  
decode: decode  
}

})();

// test @website: http://tool.oschina.net/encrypt?type=3
var s = "this is a example";
var enc = base64.encode(s);
console.log(enc);
console.log(base64.decode(enc));