base64编码和解码的js工具函数

喜欢ヅ旅行 2021-09-21 08:36 455阅读 0赞

## 上代码 ##

// 使用
    const base64 = new Base64Code()
    const str = '你好'
    const en = base64.enCode(str)
    const de = base64.deCode(en)
    console.log(en, 'base64编码') // 5L2g5aW9
    console.log(de, 'base64解码') // 你好

###### || 中文也可以进行编码, 里面已经对数据UTF-8转码再base64编码 ######

// base64函数
    function Base64Code() { 
        // base64 character set, plus padding character (=)
        var b64 = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=",
    
            // Regular expression to check formal correctness of base64 encoded strings
            b64re = /^(?:[A-Za-z\d+\/]{4})*?(?:[A-Za-z\d+\/]{2}(?:==)?|[A-Za-z\d+\/]{3}=?)?$/;
    
        // 转UTF-8格式编码 private method for UTF-8 encoding
        const utf8Encode = function (str) { 
            let string = str;
            string = string.replace(/\r\n/g, '\n');
            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;
        };
    
        // 解UTF-8格式编码 private method for UTF-8 decoding
        const utf8Decode = function (utfText) { 
            let string = '';
            let i = 0;
            let c = 0;
            let c2 = 0;
            let 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;
        };
        
        // base64编码
        this.enCode = function(string) { 
            string = utf8Encode(String(string));
            var bitmap, a, b, c,
                result = "",
                i = 0,
                rest = string.length % 3; // To determine the final padding
    
            for (; i < string.length;) { 
                if ((a = string.charCodeAt(i++)) > 255 ||
                    (b = string.charCodeAt(i++)) > 255 ||
                    (c = string.charCodeAt(i++)) > 255)
                    throw new TypeError("Failed to execute 'btoa' on 'Window': The string to be encoded contains characters outside of the Latin1 range.");
    
                bitmap = (a << 16) | (b << 8) | c;
                result += b64.charAt(bitmap >> 18 & 63) + b64.charAt(bitmap >> 12 & 63) +
                    b64.charAt(bitmap >> 6 & 63) + b64.charAt(bitmap & 63);
            }
    
            // If there's need of padding, replace the last 'A's with equal signs
            return rest ? result.slice(0, rest - 3) + "===".substring(rest) : result;
        };
    
        // base64解码
        this.deCode = function(string) { 
            // atob can work with strings with whitespaces, even inside the encoded part,
            // but only \t, \n, \f, \r and ' ', which can be stripped.
            string = String(string).replace(/[\t\n\f\r ]+/g, "");
            if (!b64re.test(string))
                throw new TypeError("Failed to execute 'atob' on 'Window': The string to be decoded is not correctly encoded.");
    
            // Adding the padding if missing, for semplicity
            string += "==".slice(2 - (string.length & 3));
            var bitmap, result = "",
                r1, r2, i = 0;
            for (; i < string.length;) { 
                bitmap = b64.indexOf(string.charAt(i++)) << 18 | b64.indexOf(string.charAt(i++)) << 12 |
                    (r1 = b64.indexOf(string.charAt(i++))) << 6 | (r2 = b64.indexOf(string.charAt(i++)));
    
                result += r1 === 64 ? String.fromCharCode(bitmap >> 16 & 255) :
                    r2 === 64 ? String.fromCharCode(bitmap >> 16 & 255, bitmap >> 8 & 255) :
                    String.fromCharCode(bitmap >> 16 & 255, bitmap >> 8 & 255, bitmap & 255);
            }
            return utf8Decode(result);
        };
    }