创建多个Ajax XMLHttpRequest（）调用

Question

I would like to display startups from the Crunchbase API (REST API) via a URL with PHP. To retrieve the json data I am using Ajax to provide a asynchronous request. The first function ajaxLoad(page, search); will do the first xmlhttp - XMLHttpRequest() to get the "permalink" - var permalink = json_de.data.items[c].properties.permalink; that is used by the second xmlhttp2 - XMLHttpRequest() which is NOT asynchronous. The second request will provide further information about the specific startup (var permalink = "kickstarter" for example). I only want to display startups which are founded after 2000-01-01 (unixtime >= 946684800). My current code works but I would like that both request are asynchronous.

How do I create two asynchronous requests? Or is there a more elegant way to carry out this task? Currently the loading time is VERY high.

It takes about 1 minute to loop through 20 startups. Could that be done faster? Thanks for the help.

function ajaxLoad(page, search) {
var xmlhttp = new XMLHttpRequest();
xmlhttp.onreadystatechange = function () {
    if (xmlhttp.readyState == 4 && xmlhttp.status == 200) { <?php
        if (isset($_GET['company'])) { ?>
            makeCompanyTable(xmlhttp.responseText); <?php
        } else { ?>
            makeATable(xmlhttp.responseText); <?php
        } ?>
    }
}
xmlhttp.open("GET", "get_json.php?p=" + page + "&search=" + search + "&company=<?php echo $companyvar; ?>", true);
xmlhttp.send(); }

function makeATable(json) {
var json_de = JSON.parse(json);
var count = Object.keys(json_de.data.items).length
var c = 0;
var val = "";
var col_counter = 1;     

while (c != count) {
    var xmlhttp2 = new XMLHttpRequest();
    var permalink = json_de.data.items[c].properties.permalink;
    xmlhttp2.open("GET", "get_org.php?permalink="+ permalink, false);
    xmlhttp2.send();
    var json_com = JSON.parse(xmlhttp2.responseText); // Ganze info des jeweiligen Startup
    var founding_date = json_com.data.properties.founded_on;
    var unixtime = Date.parse(founding_date)/1000;

    if (unixtime >= 946684800) {
        val = val + '<div class="card profile-view"><div class="pv-header"><img src="';
        var cln = "";
        cln = cln + json_de.data.items[c].properties.profile_image_url;
        if (cln == "" || cln.length <= 0) {
            val = val + "img/does_not_exist.png";
        } else {
            val = val + json_de.data.items[c].properties.profile_image_url;
        }
        val = val + '" class="pv-main" alt=""></div><div class="pv-body"><h2>';
        val = val + json_de.data.items[c].properties.name;
        cl = json_de.data.items[c].properties.short_description;
        val = val + '</h2><small';
        val = val + '>';
        val = val + json_de.data.items[c].properties.short_description;
        val = val + '</small><a href="startup.php?company=' + json_de.data.items[c].properties.permalink + '" class="pv-follow-btn">Anzeigen</a></div></div>';
        //alert(val);
        document.getElementById("col_"+col_counter).innerHTML += val;
        val = "";
        col_counter++;
        if(col_counter == 7){
            col_counter = 1;
        }
    }
    c++;
} }

Answer 1

Yes, you can make assync request. But, since you want to do it under a loop it might create problems to the code used after the request inside the loop itself. So, it is better if you go with the same code