Base64

脚本说明:
把如下代码加入<body>区域中
<script language=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) {
	/* 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))
}
</script>
<H1>Base64</H1>
<FORM NAME="f">
原码<BR>
<TEXTAREA NAME="source" ROWS=4 COLS=60 WRAP="soft">

Base64 encode

Base64 decode