Implement BASE64_ENCODE and BASE64_DECODE in JS (instance code)

Copy codeThe Code is as follows:
<Script language = 'javascript '>
/* Utf. js-UTF-8 <=> UTF-16 convertion
*
* Copyright (C) 1999 Masanao Izumo <iz@onicos.co.jp>
* Version: 1.0
* LastModified: Dec 25 1999.
* This library is free. You can redistribute it and/or modify it.
*/

/*
* Interfaces:
* Utf8 = utf16to8 (utf16 );
* Utf16 = utf16to8 (utf8 );
*/

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:
// 0 xxxxxxx
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;
}

/* Copyright (C) 1999 Masanao Izumo <iz@onicos.co.jp>
* Version: 1.0
* LastModified: Dec 25 1999.
* This library is free. You can redistribute it and/or modify it.
*/

/*
* Interfaces:
* B64 = base64encode (data );
* Data = base64decode (b64 );
*/

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,-1,-62,-1, -1,-1, 63,
52, 53, 54, 55, 56, 57, 58, 59, 60, 61,-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;
}
// Input base64 encode
Function strdecode (str ){
Return utf8to16 (base64decode (str ));
}