binary 与 base64

 1 const charsMap = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/'.split('');
 2 
 3 function binaryToBase64(chars) {
 4     const padLength = 3 - chars.length % 3;
 5     return (chars.split('').map(char => {
 6         return char.charCodeAt(0).toString(2).padStart(8, '0');
 7     }).join('') + '0'.repeat(2 * padLength)).split(/\B(?=(?:\d{6})+$)/g).map(char => {
 8         return charsMap[+('0b' + char)];
 9     }).join('') + '='.repeat(padLength);
10 }
11 
12 function base64ToBinary(base64) {
13     const tail = base64.match(/=+/);
14     const padLength = tail ? tail[0].length : 0;
15     return base64.slice(0, -padLength).split('').map(char => {
16         return charsMap.indexOf(char).toString(2).padStart(6, '0');
17     }).join('').slice(0, -padLength * 2).split(/\B(?=(?:\d{8})+$)/g).map(code => {
18         return String.fromCharCode(+('0b' + code));
19     }).join('');
20 }
21 
22 export {
23     binaryToBase64,
24     base64ToBinary
25 }