javascript 实现Base64加密

想必大家对base64并不陌生吧，在本文将为大家介绍下Js中的base64加密解密过程，感兴趣的朋友不要错过

<script type="text/javascript">  
 
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) {  
 
do {  
c1 = base64decodechars[str.charCodeAt(i++) & 0xff];  
} while (i < len && c1 == -1);  
if (c1 == -1)  
break;  
 
do {  
c2 = base64decodechars[str.charCodeAt(i++) & 0xff];  
} while (i < len && c2 == -1);  
if (c2 == -1)  
break;  
 
out += String.fromCharCode((c1 << 2) | ((c2 & 0x30) >> 4));  
 
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));  
 
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;  
}  
</script>