Looking for assistance with getting 2 functions to run onLoad using Ajax - currently only 1 is operational

In the coding journey, I first implemented shuffle functions for arrays which was successful. Then, I proceeded to define two global variables that would dictate the random order in which images are displayed on the webpage. The variable picOrder was meant to be a simple array ranging from 0 to picCount, with the actual value of picCount determined by an Ajax call during page load. However, there seemed to be an issue as the picOrder array was not being properly set even though picCount was successfully retrieved. Interestingly, manually running "arrangePics();" in the console worked perfectly as it populated and shuffled the picOrder array. Unfortunately, simply placing calls to both functions inside "" or enclosing them within the "doStuff()" function did not yield the desired results.

Array.prototype.shuffle = function() {
var s = [];
while (this.length) s.push(this.splice(Math.random() * this.length, 1)[0]);
while (s.length) this.push(s.pop());
return this;
}

var picOrder = new Array();
var picCount;

function getPicCount() {
//  picCount = array(10);
    if (window.XMLHttpRequest) {// code for IE7+, Firefox, Chrome, Opera, Safari
      xmlhttp=new XMLHttpRequest();
      } else {// code for IE6, IE5
      xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");
      }
    xmlhttp.onreadystatechange=function() {
      if (xmlhttp.readyState==4 && xmlhttp.status==200) {
            picCount = xmlhttp.responseText;
        }
      }
    xmlhttp.open("GET","/example.com/images.php?count=hello",true);
    xmlhttp.send();
    //picCount.shuffle;

}

function arrangePics() {
    for(var i = 0;i<picCount;i++) {
    picOrder[i] = i;
    }
    picOrder.shuffle();
    //alert(picOrder);
}

HTML

<body onLoad="getPicCount();arrangePics();">

or

<body onLoad="doStuff();">

Answer №1

To ensure proper functionality, be sure to execute the arrangePics() function only after the asynchronous AJAX call has successfully returned. This means you should include it within the

if (xmlhttp.readyState==4 && xmlhttp.status==200) {}
block to guarantee that all data has been fully received before arranging the pictures.

The issue currently arises from JavaScript calling getPicCount();arrangePics(); sequentially. Since the first method triggers the AJAX request and returns immediately, the second method attempts to arrange zero pictures. By manually running arrangePics() in the console, it introduces a delay that allows the AJAX call to finish, setting the expected picCount.

To resolve this issue, update the callback function to:

if (xmlhttp.readyState==4 && xmlhttp.status==200) {
    picCount = xmlhttp.responseText;

    for(var i = 0;i<picCount;i++) {
        picOrder[i] = i;
    }
    picOrder.shuffle();
}

This adjustment will properly shuffle the pictures once the count has been retrieved from the server.

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