本文实例讲述了JS实现的base64加密解密。分享给大家供大家参考，具体如下：

完整的代码：

var base64EncodeChars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

var base64DecodeChars = new Array(

-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,

-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,

-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, -1, -1, 63,

52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -1, -1, -1,

-1,　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, -1, -1, -1, -1, -1,

-1, 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, -1, -1, -1, -1, -1);

var base64EncodeChars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

var base64DecodeChars = new Array(

-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,

-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,

-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, -1, -1, 63,

52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -1, -1, -1,

-1,　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, -1, -1, -1, -1, -1,

-1, 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, -1, -1, -1, -1, -1);

function base64encode(str) {

var out, i, len;

var c1, c2, c3;

len = str.length;

i = 0;

out = "";

while(i < len) {

c1 = str.charCodeAt(i++) & 0xff;

if(i == len)

{

out += base64EncodeChars.charAt(c1 >> 2);

out += base64EncodeChars.charAt((c1 & 0x3) << 4);

out += "==";

break;

}

c2 = str.charCodeAt(i++);

if(i == len)

{

out += base64EncodeChars.charAt(c1 >> 2);

out += base64EncodeChars.charAt(((c1 & 0x3)<< 4) | ((c2 & 0xF0) >> 4));

out += base64EncodeChars.charAt((c2 & 0xF) << 2);

out += "=";

break;

}

c3 = str.charCodeAt(i++);

out += base64EncodeChars.charAt(c1 >> 2);

out += base64EncodeChars.charAt(((c1 & 0x3)<< 4) | ((c2 & 0xF0) >> 4));

out += base64EncodeChars.charAt(((c2 & 0xF) << 2) | ((c3 & 0xC0) >>6));

out += base64EncodeChars.charAt(c3 & 0x3F);

}

return out;

}

function base64decode(str) {

var c1, c2, c3, c4;

var i, len, out;

len = str.length;

i = 0;

out = "";

while(i < len) {

/* c1 */

do {

c1 = base64DecodeChars[str.charCodeAt(i++) & 0xff];

} while(i < len && c1 == -1);

if(c1 == -1)

break;

/* c2 */

do {

c2 = base64DecodeChars[str.charCodeAt(i++) & 0xff];

} while(i < len && c2 == -1);

if(c2 == -1)

break;

out += String.fromCharCode((c1 << 2) | ((c2 & 0x30) >> 4));

/* c3 */

do {

c3 = str.charCodeAt(i++) & 0xff;

if(c3 == 61)

return out;

c3 = base64DecodeChars[c3];

} while(i < len && c3 == -1);

if(c3 == -1)

break;

out += String.fromCharCode(((c2 & 0XF) << 4) | ((c3 & 0x3C) >> 2));

/* c4 */

do {

c4 = str.charCodeAt(i++) & 0xff;

if(c4 == 61)

return out;

c4 = base64DecodeChars[c4];

} while(i < len && c4 == -1);

if(c4 == -1)

break;

out += String.fromCharCode(((c3 & 0x03) << 6) | c4);

}

return out;

}

function utf16to8(str) {

var out, i, len, c;

out = "";

len = str.length;

for(i = 0; i < len; i++) {

c = str.charCodeAt(i);

if ((c >= 0x0001) && (c <= 0x007F)) {

out += str.charAt(i);

} else if (c > 0x07FF) {

out += String.fromCharCode(0xE0 | ((c >> 12) & 0x0F));

out += String.fromCharCode(0x80 | ((c >>　6) & 0x3F));

out += String.fromCharCode(0x80 | ((c >>　0) & 0x3F));

} else {

out += String.fromCharCode(0xC0 | ((c >>　6) & 0x1F));

out += String.fromCharCode(0x80 | ((c >>　0) & 0x3F));

}

}

return out;

}

function utf8to16(str) {

var out, i, len, c;

var char2, char3;

out = "";

len = str.length;

i = 0;

while(i < len) {

c = str.charCodeAt(i++);

switch(c >> 4)

{

case 0: case 1: case 2: case 3: case 4: case 5: case 6: case 7:

// 0xxxxxxx

out += str.charAt(i-1);

break;

case 12: case 13:

// 110x xxxx　 10xx xxxx

char2 = str.charCodeAt(i++);

out += String.fromCharCode(((c & 0x1F) << 6) | (char2 & 0x3F));

break;

case 14:

// 1110 xxxx　10xx xxxx　10xx xxxx

char2 = str.charCodeAt(i++);

char3 = str.charCodeAt(i++);

out += String.fromCharCode(((c & 0x0F) << 12) |

((char2 & 0x3F) << 6) |

((char3 & 0x3F) << 0));

break;

}

}

return out;

}

function doit() {

var f = document.f

f.output.value = base64encode(utf16to8(f.source.value))

f.decode.value = utf8to16(base64decode(f.output.value))

}

Base64

原码

Base64 encode

Base64 decode

关于base64加密解密还可参看本站在线工具：

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希望本文所述对大家JavaScript程序设计有所帮助。