1460918894977.js

'use strict';
const http = require('http');

const originalString = 'Today we see a good accelerator: http://alchemistaccelerator.com, you can found some thing in the wikipedia, https://en.wikipedia.org/wiki/The_Alchemist_Accelerator. or google it by : https://www.google.com.hk/search?es_sm=91&q=alchemist+accelerator&oq=alchemist+a&gs_l=serp.3.2.0l10.233056.233264.0.235425.2.2.0.0.0.0.134.267.0j2.2.0....0...1c.1j4.64.serp..0.2.265.J6dlgO9eRVI';


function fn(inputString, callback) {
    // not a strict url match pattern
    var regex = /https?:\/\/[\d\w\.\/_\-\?&=+#@]+\/?/g;
    const newContent = [];
    let temp = null;
    let urlCount = 0;
    let prevIndex = 0;

    while (temp = regex.exec(inputString)) {
        newContent.push(inputString.slice(prevIndex, temp.index));
        newContent.push(temp[0]);
        prevIndex = regex.lastIndex;
        urlCount ++;
        getContent(newContent, newContent.length - 1, err => {
            // just ignore the failed urls.
            if (err) console.error('fetch url content failed ', err, err.stack);
            if (-- urlCount === 0) {
                callback && callback(newContent.join(''));
            }
        });
    }
    newContent.push(inputString.slice(prevIndex));
}

function getContent(list, index, callback) {
    let data = [];
    require(list[index].split(':')[0]).get(list[index], resp => {
        resp.on('data', chunk => data.push(chunk));
        resp.on('end', () => {
            data = Buffer.concat(data);
            list[index] = data.toString();
            callback && callback();
        })
    }).on('error', err => {
        callback && callback(err);
    })
}

/* test */
fn(originalString, res => {
    console.log(res);
});