base64的转码与解码

Posted 2023-03-13 huihuihero

handleBase64.js

// 处理base64的转码和解码
const handleBase64 = function () 
    let _keyStr ="ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";

    // base64转码
    function encode(input) 
        let output = "";
        let chr1, chr2, chr3, enc1, enc2, enc3, enc4;
        let 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;
    ;

    // base64 解码
    function 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 = _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;
    ;

    // UTF-8格式的
    function _utf8_encode(string) 
        string = string.replace(/\\r\\n/g, "\\n");
        let utftext = "";
        for (let n = 0; n < string.length; n++) 
            let 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;
    ;

    // UTF-8格式的
    function _utf8_decode(utftext) 
        let string = "";
        let i = 0;
        let 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;
    ;

    return 
        encode,
        decode,
        _utf8_encode,
        _utf8_decode,
    
()

export 
    handleBase64

使用

import  handleBase64  from "@/utils/data-handle/handleBase64.js"

handleBase64.encode("xxx")
handleBase64.decode("Lyogd3hsb2dpbi5jc3MgKi")