node.js进阶【19】：base64 编码解码

base64 编码解码

一、普通字符串 编码解码:

var b = new Buffer('JavaScript');
var s = b.toString('base64');
// SmF2YVNjcmlwdA==

var b = new Buffer('SmF2YVNjcmlwdA==', 'base64')
var s = b.toString();
// JavaScript

二、编码解码并转成hex

var b = new Buffer('SmF2YVNjcmlwdA==', 'base64')
var s = b.toString('hex');
// 4a617661536372697074

var b = new Buffer('4a617661536372697074', 'hex')
var s = b.toString('utf8');
// JavaScript

三、编码解码图片

var fs = require('fs');

// function to encode file data to base64 encoded string
function base64_encode(file) {
    // read binary data
    var bitmap = fs.readFileSync(file);
    // convert binary data to base64 encoded string
    return new Buffer(bitmap).toString('base64');
}

// function to create file from base64 encoded string
function base64_decode(base64str, file) {
    // create buffer object from base64 encoded string, it is important to tell the constructor that the string is base64 encoded
    var bitmap = new Buffer(base64str, 'base64');
    // write buffer to file
    fs.writeFileSync(file, bitmap);
    console.log('******** File created from base64 encoded string ********');
}

// convert image to base64 encoded string
var base64str = base64_encode('kitten.jpg');
console.log(base64str);
// convert base64 string back to image 
base64_decode(base64str, 'copy.jpg');