[转载] Javascript实现Base64编码与解码
1 <html> 2 <head> 3 <META HTTP-EQUIV="MSThemeCompatible" CONTENT="Yes"> 4 <meta http-equiv="Content-Type" content="text/html; charset=unicode"> 5 <script language="JavaScript" type="text/javascript" src="../var.js"></script> 6 <title>Base64 Encode and Decode</title> 7 <style> 8 </style> 9 <script type="text/javascript" language="javascript"> 10 var base64EncodeChars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"; 11 var base64DecodeChars = new Array( 12 -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 13 -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 14 -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, -1, -1, 63, 15 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -1, -1, -1, 16 -1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 17 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, -1, 18 -1, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 19 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, -1, -1, -1, -1, -1); 20 21 function base64encode(str) { 22 var out, i, len; 23 var c1, c2, c3; 24 25 len = str.length; 26 i = 0; 27 out = ""; 28 while(i < len) { 29 c1 = str.charCodeAt(i++) & 0xff; 30 if(i == len) 31 { 32 out += base64EncodeChars.charAt(c1 >> 2); 33 out += base64EncodeChars.charAt((c1 & 0x3) << 4); 34 out += "=="; 35 break; 36 } 37 c2 = str.charCodeAt(i++); 38 if(i == len) 39 { 40 out += base64EncodeChars.charAt(c1 >> 2); 41 out += base64EncodeChars.charAt(((c1 & 0x3)<< 4) | ((c2 & 0xF0) >> 4)); 42 out += base64EncodeChars.charAt((c2 & 0xF) << 2); 43 out += "="; 44 break; 45 } 46 c3 = str.charCodeAt(i++); 47 out += base64EncodeChars.charAt(c1 >> 2); 48 out += base64EncodeChars.charAt(((c1 & 0x3)<< 4) | ((c2 & 0xF0) >> 4)); 49 out += base64EncodeChars.charAt(((c2 & 0xF) << 2) | ((c3 & 0xC0) >>6)); 50 out += base64EncodeChars.charAt(c3 & 0x3F); 51 } 52 return out; 53 } 54 55 function base64decode(str) { 56 var c1, c2, c3, c4; 57 var i, len, out; 58 59 len = str.length; 60 i = 0; 61 out = ""; 62 while(i < len) { 63 /* c1 */ 64 do { 65 c1 = base64DecodeChars[str.charCodeAt(i++) & 0xff]; 66 } while(i < len && c1 == -1); 67 if(c1 == -1) 68 break; 69 70 /* c2 */ 71 do { 72 c2 = base64DecodeChars[str.charCodeAt(i++) & 0xff]; 73 } while(i < len && c2 == -1); 74 if(c2 == -1) 75 break; 76 77 out += String.fromCharCode((c1 << 2) | ((c2 & 0x30) >> 4)); 78 79 /* c3 */ 80 do { 81 c3 = str.charCodeAt(i++) & 0xff; 82 if(c3 == 61) 83 return out; 84 c3 = base64DecodeChars[c3]; 85 } while(i < len && c3 == -1); 86 if(c3 == -1) 87 break; 88 89 out += String.fromCharCode(((c2 & 0XF) << 4) | ((c3 & 0x3C) >> 2)); 90 91 /* c4 */ 92 do { 93 c4 = str.charCodeAt(i++) & 0xff; 94 if(c4 == 61) 95 return out; 96 c4 = base64DecodeChars[c4]; 97 } while(i < len && c4 == -1); 98 if(c4 == -1) 99 break; 100 out += String.fromCharCode(((c3 & 0x03) << 6) | c4); 101 } 102 return out; 103 } 104 105 function utf16to8(str) { 106 var out, i, len, c; 107 108 out = ""; 109 len = str.length; 110 for(i = 0; i < len; i++) { 111 c = str.charCodeAt(i); 112 if ((c >= 0x0001) && (c <= 0x007F)) { 113 out += str.charAt(i); 114 } else if (c > 0x07FF) { 115 out += String.fromCharCode(0xE0 | ((c >> 12) & 0x0F)); 116 out += String.fromCharCode(0x80 | ((c >> 6) & 0x3F)); 117 out += String.fromCharCode(0x80 | ((c >> 0) & 0x3F)); 118 } else { 119 out += String.fromCharCode(0xC0 | ((c >> 6) & 0x1F)); 120 out += String.fromCharCode(0x80 | ((c >> 0) & 0x3F)); 121 } 122 } 123 return out; 124 } 125 126 function utf8to16(str) { 127 var out, i, len, c; 128 var char2, char3; 129 130 out = ""; 131 len = str.length; 132 i = 0; 133 while(i < len) { 134 c = str.charCodeAt(i++); 135 switch(c >> 4) 136 { 137 case 0: case 1: case 2: case 3: case 4: case 5: case 6: case 7: 138 // 0xxxxxxx 139 out += str.charAt(i-1); 140 break; 141 case 12: case 13: 142 // 110x xxxx 10xx xxxx 143 char2 = str.charCodeAt(i++); 144 out += String.fromCharCode(((c & 0x1F) << 6) | (char2 & 0x3F)); 145 break; 146 case 14: 147 // 1110 xxxx 10xx xxxx 10xx xxxx 148 char2 = str.charCodeAt(i++); 149 char3 = str.charCodeAt(i++); 150 out += String.fromCharCode(((c & 0x0F) << 12) | 151 ((char2 & 0x3F) << 6) | 152 ((char3 & 0x3F) << 0)); 153 break; 154 } 155 } 156 157 return out; 158 } 159 160 function CharToHex(str) { 161 var out, i, len, c, h; 162 163 out = ""; 164 len = str.length; 165 i = 0; 166 while(i < len) 167 { 168 c = str.charCodeAt(i++); 169 h = c.toString(16); 170 if(h.length < 2) 171 h = "0" + h; 172 173 out += "\\x" + h + " "; 174 if(i > 0 && i % 8 == 0) 175 out += "\r\n"; 176 } 177 178 return out; 179 } 180 181 function doEncode() { 182 var src = document.getElementById('src').value; 183 document.getElementById('dest').value = base64encode(utf16to8(src)); 184 } 185 186 function doDecode() { 187 var src = document.getElementById('src').value; 188 var opts = document.getElementById('opt'); 189 190 if(opts.checked) 191 { 192 document.getElementById('dest').value = CharToHex(base64decode(src)); 193 } 194 else 195 { 196 document.getElementById('dest').value = utf8to16(base64decode(src)); 197 } 198 } 199 200 </script> 201 </head> 202 203 <BODY bgcolor="#EAF0F8" topmargin="10" leftmargin="10" rightmargin="10" bottommargin="10"> 204 <div id="contain" style="font-family: Tahoma, Arial; font-size:11pt"> 205 <div id="mainbg"> 206 <div style="color: #000080; margin-bottom: 10"><b>Base64 Encode / Decode</b></div> 207 <div> 208 <textarea id="src" rows=6 cols=60 value="" name="src" style="font-family: Consolas; font-size: 16px;" onmouseover="this.focus();this.select()"></textarea> 209 <div style="margin: 10 0 10 0"> 210 <input onclick="doEncode();" type=button value="Encode" name="encode"> 211 <input onclick="doDecode();" type=button value="Decode" name="decode"> 212 <input type="checkbox" value="hex" name="opt" id="opt">Hex 213 </div> 214 <textarea id="dest" rows=6 cols=60 value="" name="dest" style="font-family: Consolas; font-size: 16px;" onmouseover="this.focus();this.select()"></textarea> 215 </div> 216 </div> 217 </div> 218 </BODY> 219 </html> 220
来源：http://www.cnblogs.com/youring2/archive/2013/03/04/2942880.html
