binary 与 base64

const charsMap = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/'.split('');

function binaryToBase64(chars) {
    const padLength = (3 - chars.length % 3) % 3;
    return (chars.split('').map(char => {
        return char.charCodeAt(0).toString(2).padStart(8, '0');
    }).join('') + '0'.repeat(2 * padLength)).split(/\B(?=(?:\d{6})+$)/g).map(char => {
        return charsMap[+('0b' + char)];
    }).join('') + '='.repeat(padLength);
}

function base64ToBinary(base64) {
    const tail = base64.match(/=+/);
    const padLength = tail ? tail[0].length : 0;
    return base64.slice(0, base64.length - padLength).split('').map(char => {
        return charsMap.indexOf(char).toString(2).padStart(6, '0');
    }).join('').slice(0, base64.length * 6 - padLength * 8).split(/\B(?=(?:\d{8})+$)/g).map(code => {
        return String.fromCharCode(+('0b' + code));
    }).join('');
}

export {
    binaryToBase64,
    base64ToBinary
}