标题：原生JS对字符串进行base64编码/解码
出处：刘新修
时间：Fri, 23 Oct 2015 13:54:18 +0000
作者：刘新修
地址：http://liuxinxiu.com:80/base64_JS/

内容：
JavaScript代码
/**** 下面是64个基本的编码 ****/  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);  /**** 编码的方法 ****/  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;  };  /**** 解码的方法 ****/  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;  };  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;  };    /** 编码 **/  /** val=base64encode(utf16to8(src)); **/    /** 解码 **/  /** val=utf8to16(base64decode(src)); **/  /** var d="PGgxPjExMTwvaDE+PGRpdiBjbGFzcz0ibmFtZSI+MTEyMjwvZGl2Pg=="; **/  



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