js base64的实现

什么是base64

base64是用规定的64种字符来表示任意二进制数据的一种编码格式，而且这64种字符均是可见字符，而之所以要是可见的是因为在不同设备上处理不可见字符时可能发生错误。通常，电子邮件数据、公钥证书会经常使用。

base64编码不提供加密，只是将一种形式的数据转化为另一种形式。 Base64编码使用二进制表示，字符串的每一个字符由8个字节表示。

Js实现base64

//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：

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(/\
\
/g,"\
");  
        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;  
    }  
}

typescript 的写法

export class Base64 {

  // private property
  private _keyStr = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=';

  // public method for encoding
  encode(input) {
    let output = '';
    let chr1, chr2, chr3, enc1, enc2, enc3, enc4;
    let i = 0;
    input = this._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 +
        this._keyStr.charAt(enc1) + this._keyStr.charAt(enc2) +
        this._keyStr.charAt(enc3) + this._keyStr.charAt(enc4);
    }
    return output;
  }

  // public method for decoding
  decode(input) {
    let output = '';
    let chr1, chr2, chr3;
    let enc1, enc2, enc3, enc4;
    let i = 0;
    input = input.replace(/[^A-Za-z0-9\+\/\=]/g, '');
    while (i < input.length) {
      enc1 = this._keyStr.indexOf(input.charAt(i++));
      enc2 = this._keyStr.indexOf(input.charAt(i++));
      enc3 = this._keyStr.indexOf(input.charAt(i++));
      enc4 = this._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 = this._utf8_decode(output);
    return output;
  }

  // private method for UTF-8 encoding
  private _utf8_encode(string) {
    string = string.replace(/\
\
/g, '\
');
    let utftext = '';
    for (let n = 0; n < string.length; n++) {
      const 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
  private _utf8_decode(utftext) {
    let string = '';
    let i = 0;
    let c = 0, c2 = 0, c3 = 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;
  }
}

本文内容仅供个人学习、研究或参考使用，不构成任何形式的决策建议、专业指导或法律依据。未经授权，禁止任何单位或个人以商业售卖、虚假宣传、侵权传播等非学习研究目的使用本文内容。如需分享或转载，请保留原文来源信息，不得篡改、删减内容或侵犯相关权益。感谢您的理解与支持！

链接: https://shenqiku.cn/article/FLY_3559