一、内置函数

内置函数：btoa

let value = 'hello';
console.log(btoa(value));

内置函数：atob

let value = 'aGVsbG8=';
console.log(atob(value));

二、借助第三方库实现，例如CryptoJS

const CryptoJS = require("crypto-js");
let value = "hello";
let trans = CryptoJS.enc.Utf8.parse(value);
let encrypted = CryptoJS.enc.Base64.stringify(trans);
console.log(encrypted)

//自己编写一套Base64编码和解码算法

function Base64(){
	this.encode = function(val){
		//编码逻辑
		return val
	}
	this.decode = function(val){
		//解码逻辑
		return val
	}
}
encrypt = new Base64();
console.log(encrypt.encode("encode"))