原生js的base64和node.js的base64及btoa实现

1.原生js封装的base64

function Base64() { 
 // private property 
 _keyStr = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/="; 
  
 // public method for encoding 
 this.encode = function (input) { 
  var output = ""; 
  var chr1, chr2, chr3, enc1, enc2, enc3, enc4; 
  var i = 0; 
  input = _utf8_encode(input); 
  while (i < input.length) { 
   chr1 = input.charCodeAt(i++); 
   chr2 = input.charCodeAt(i++); 
   chr3 = input.charCodeAt(i++); 
   enc1 = chr1 >> 2; 
   enc2 = ((chr1 & 3) << 4) | (chr2 >> 4); 
   enc3 = ((chr2 & 15) << 2) | (chr3 >> 6); 
   enc4 = chr3 & 63; 
   if (isNaN(chr2)) { 
    enc3 = enc4 = 64; 
   } else if (isNaN(chr3)) { 
    enc4 = 64; 
   } 
   output = output + 
   _keyStr.charAt(enc1) + _keyStr.charAt(enc2) + 
   _keyStr.charAt(enc3) + _keyStr.charAt(enc4); 
  } 
  return output; 
 } 
  
 // public method for decoding 
 this.decode = function (input) { 
  var output = ""; 
  var chr1, chr2, chr3; 
  var enc1, enc2, enc3, enc4; 
  var i = 0; 
  input = input.replace(/[^A-Za-z0-9\+\/\=]/g, ""); 
  while (i < input.length) { 
   enc1 = _keyStr.indexOf(input.charAt(i++)); 
   enc2 = _keyStr.indexOf(input.charAt(i++)); 
   enc3 = _keyStr.indexOf(input.charAt(i++)); 
   enc4 = _keyStr.indexOf(input.charAt(i++)); 
   chr1 = (enc1 << 2) | (enc2 >> 4); 
   chr2 = ((enc2 & 15) << 4) | (enc3 >> 2); 
   chr3 = ((enc3 & 3) << 6) | enc4; 
   output = output + String.fromCharCode(chr1); 
   if (enc3 != 64) { 
    output = output + String.fromCharCode(chr2); 
   } 
   if (enc4 != 64) { 
    output = output + String.fromCharCode(chr3); 
   } 
  } 
  output = _utf8_decode(output); 
  return output; 
 } 
  
 // private method for UTF-8 encoding 
 _utf8_encode = function (string) { 
  string = string.replace(/\r\n/g,"\n"); 
  var utftext = ""; 
  for (var n = 0; n < string.length; n++) { 
   var c = string.charCodeAt(n); 
   if (c < 128) { 
    utftext += String.fromCharCode(c); 
   } else if((c > 127) && (c < 2048)) { 
    utftext += String.fromCharCode((c >> 6) | 192); 
    utftext += String.fromCharCode((c & 63) | 128); 
   } else { 
    utftext += String.fromCharCode((c >> 12) | 224); 
    utftext += String.fromCharCode(((c >> 6) & 63) | 128); 
    utftext += String.fromCharCode((c & 63) | 128); 
   } 
  
  } 
  return utftext; 
 } 
  
 // private method for UTF-8 decoding 
 _utf8_decode = function (utftext) { 
  var string = ""; 
  var i = 0; 
  var c = c1 = c2 = 0; 
  while ( i < utftext.length ) { 
   c = utftext.charCodeAt(i); 
   if (c < 128) { 
    string += String.fromCharCode(c); 
    i++; 
   } else if((c > 191) && (c < 224)) { 
    c2 = utftext.charCodeAt(i+1); 
    string += String.fromCharCode(((c & 31) << 6) | (c2 & 63)); 
    i += 2; 
   } else { 
    c2 = utftext.charCodeAt(i+1); 
    c3 = utftext.charCodeAt(i+2); 
    string += String.fromCharCode(((c & 15) << 12) | ((c2 & 63) << 6) | (c3 & 63)); 
    i += 3; 
   } 
  } 
  return string; 
 } 
} 

使用方法

var base64 = new Base64(); 
var result = base64.encode("中文内容"); 
//解密
var result2 = base64.decode(result); 

2.node.js的base64 //假btoa

function btoa(str){
     return new Buffer.from(str, 'utf-8').toString('base64')
}
function atob(str){
    return new Buffer.from(str, 'base64').toString('utf-8')
}

3.node.js实现btoa //binary

function btoa(str){
     return new Buffer.from(str, "binary").toString("base64")
}

function atob(str){
     return new Buffer.from(str, "base64").toString("binary")
}

4.原生js.乐易编译助手拷贝的btoa

PADCHAR = "=", ALPHA = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/", getbyte = function(t, e) {
    var i = t.charCodeAt(e);
    if (i > 255) throw "INVALID_CHARACTER_ERR: DOM Exception 5";
    return i
}
btoa = function(t) {
    if (1 != arguments.length) throw "SyntaxError: Not enough arguments";
    var e, i, n = PADCHAR,
        o = ALPHA,
        p = getbyte,
        r = [];
    t = "" + t;
    var s = t.length - t.length % 3;
    if (0 == t.length) return t;
    for (e = 0; e < s; e += 3)
    i = p(t, e) << 16 | p(t, e + 1) << 8 | p(t, e + 2), r.push(o.charAt(i >> 18)), r.push(o.charAt(i >> 12 & 63)), r.push(o.charAt(i >> 6 & 63)), r.push(o.charAt(63 & i));
    switch (t.length - s) {
        case 1:
            i = p(t, e) << 16, r.push(o.charAt(i >> 18) + o.charAt(i >> 12 & 63) + n + n);
            break;
        case 2:
            i = p(t, e) << 16 | p(t, e + 1) << 8, r.push(o.charAt(i >> 18) + o.charAt(i >> 12 & 63) + o.charAt(i >> 6 & 63) + n)
    }
    return r.join("")
}