base64 编码原理解析

Question

let str = '百度'
let buf = Buffer.from(str);
// console.log(buf) // <Buffer e7 99 be e5 ba a6>

console.log((0xe7).toString(2)) // 11100111
console.log((0x99).toString(2)) // 10011001
console.log((0xbe).toString(2)) // 10111110
console.log((0xe5).toString(2)) // 11100101
console.log((0xba).toString(2)) // 10111010
console.log((0xa6).toString(2)) // 10100110
// 111001111001100110111110111001011011101010100110

// 111001 111001 100110 111110 111001 011011 101010 100110

console.log(parseInt('00111001', 2)) // 57
console.log(parseInt('00111001', 2)) // 57
console.log(parseInt('00100110', 2)) // 38
console.log(parseInt('00111110', 2)) // 62
console.log(parseInt('00111001', 2)) // 57
console.log(parseInt('00011011', 2)) // 27
console.log(parseInt('00101010', 2)) // 42
console.log(parseInt('00100110', 2)) // 38

let base = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/'

console.log(base[57]+base[57]+base[38]+base[62]+base[57]+base[27]+base[42]+base[38])

// 55m+5bqm