javascript base64 encode decode 支持中文

* 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));