js的Base64编码与解码

js的Base64编码与解码

pc和手机app项目中，经常需要将手机自带的表情图片转换特定的编码格式与后台进行交互。

Base64其实是一种简单的置换加密方式，但是BASE64的用处往往并不是为了防止信息泄露，而且为了方便传输。

如何使用Base64进行加密解密：

1.加密解密方法使用：

//1.加密
var str = '124中文内容';
var base = new Base64();
var result = base.encode(str);
//document.write(result);
//2.解密
var result2 = base.decode(result);
document.write(result2);

2.加密、解密算法封装：

/**
*
* Base64 encode / decode
*
* @author haitao.tu
* @date  2010-04-26
* @email [e-mail]
*
*/
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;
  }
}

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作者：kerryqpw
来源：****
原文：https://blog.****.net/kerryqpw/article/details/77844576
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