我们知道，浏览器的window对象提供有window.atob()和window.btoa()方法可以对字符串进行Base64编码和解码。
console.log(window.btoa(window.atob('yanggb')));
但是有些运行环境，比如nuxt的服务端环境没法使用window对象(window对象只有在浏览器的运行环境中才存在)，所以需要自己实现一个Base64的编码解码功能，下面是用原生JavaScript实现该功能，可以作为一个常用工具使用。
UTF-8编码的函数
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解码的函数
function utf8_decode (utfText) {
let string = "";
let i = 0;
let c = 0;
let c1 = 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编码的函数
export const 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 +
input.charAt(enc1) + input.charAt(enc2) +
input.charAt(enc3) + input.charAt(enc4);
}
return output;
}
Base64解码的函数
export const 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 = input.indexOf(input.charAt(i++));
enc2 = input.indexOf(input.charAt(i++));
enc3 = input.indexOf(input.charAt(i++));
enc4 = input.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;
}
