Develop Reference

Need to access an element by id which isn't accessible until after document.load

I am using an external server to load a widget on my page. I want to access that getElementById after it loads. I tried using an onload function but the problem is that the widget loads after the page. Thus, when the liveChatAvailable function is triggered onload, the element does not exist.
Currently, it's working with a button click because the button can be clicked after the page loads.
This is the code loading the liveChat.
<script type='text/javascript' data-cfasync='false'>
window.purechatApi = {
l: [],
t: [],
on: function () {
this.l.push(arguments);
}
};
(function () {
var done = false;
var script = document.createElement('script');
script.async = true;
script.type = 'text/javascript';
script.src = 'https://app.purechat.com/VisitorWidget/WidgetScript';
document.getElementsByTagName('HEAD').item(0).appendChild(script);
script.onreadystatechange = script.onload = function (e) {
if (!done && (!this.readyState || this.readyState == 'loaded' || this.readyState == 'complete')) {
var w = new PCWidget(
{
c: '<CODEXXXX>', f: true
});
done = true; liveChatAvailable();
} }; })();
</script>
This is the code accessing element by ID.
<script>
function liveChatAvailable() {
var liveChat = document.getElementById("PureChatWidget");
if((liveChat.className).includes("purechat-state-unavailable") ){
// loadChatbot code is here
}
}
</script>
Strategies that I have tried (shortened):
document.body.onload ...
document.onload ...
body onload = ....
window.AddEventListener ('DOMContentLoaded ...

Cannot call function from dynamically loaded javascript file

I'm loading a javascript external file from another javascript file present in the document and since its loaded, I want to call a function from the loaded js file.
Here is the load function:
function loadScript(url) {
var head = window.top.document.getElementsByTagName('head')[0];
var script = window.top.document.createElement('script');
script.src = url;
script.type= "text/javascript";
head.appendChild(script);
if(script.readyState) { //IE
script.onreadystatechange = function() {
if ( script.readyState === "loaded" || script.readyState === "complete" ) {
script.onreadystatechange = null;
console.log("[BANDEAU] script loaded");
testAlert();
}
};
} else { //Others
script.onload = function() {
console.log("[BANDEAU] script loaded");
testAlert();
};
}
}
So it works nice because the javascript file is succesfuly loaded but I cannot access the testAlert() method from the loaded javascript file, as I try in the code above, right after printing that the script is loaded. When I try to get the type of the function with typeOf on window[testAlert], I get an undefined. But when I try to execute the testAlert() method in the developer console, it works perfectly. Does anyone see what I'm doing wrong ?
Does the position in the DOM between the caller javascript file and the loaded javascript file might be the reason ?

You need to assign the load handlers BEFORE changing the src
function loadScript(url) {
var head = document.getElementsByTagName('head')[0]; // window.top in frames/iFrames
var script = document.createElement('script');
script.type = "text/javascript";
if (script.readyState) { //IE
script.onreadystatechange = function() {
if (script.readyState === "loaded" || script.readyState === "complete") {
script.onreadystatechange = null;
console.log("[BANDEAU] script loaded");
testAlert(); // window.top.testAlert() if needed
}
};
}
else {
script.onload = function() {
console.log("[BANDEAU] script loaded");
testAlert(); // window.top.testAlert() if needed
};
}
script.src = url;
head.appendChild(script);
}

In addition to what mplungjan said, I'm pretty sure you'd have to do an eval() on the loaded script in order to have a legitimate address for the call to testAlert().
Also, check out this link for more info.

Load an external JS file from a JS class

I use an external js file on my site, it currently sits at the bottom of my boilerplate.
<script type="text/javascript" src="https://maps.googleapis.com/maps/api/js?libraries=places"></script>
I only need to load this script on specific pages or when a specific modal loads.
Is there a way to call the script from my javascript code. For example:
$(document).one('opened.fndtn.reveal', '#my-modal[data-reveal]', function () {
//load places api
});
Also Google suggest having it on every page - why is this? I do not need to use it on every page.

You can use .getScript()
Load a JavaScript file from the server using a GET HTTP request, then execute it.
$.getScript("https://maps.googleapis.com/maps/api/js?libraries=places", function(){
alert("script loaded");
});

Another way if you don't have jQuery.
function inyectScript(url, success){
var script = document.createElement('script');
script.src = url;
script.id = "myScript";
var done = false;
script.onload = script.onreadystatechange = function() {
if (!done && (!this.readyState || this.readyState === 'loaded' || this.readyState === 'complete')) {
done = true;
success();
script.onload = script.onreadystatechange = null;
}
};
document.getElementsByTagName('head')[0].appendChild(script);
}

Load jQuery dynamically and use it

How to correctly load jQuery library if it is not loaded yet?
somepage.html:
<script src="http://example.com/js/widget_init.js" type="text/javascript"></script>
<script type="text/javascript">
if (typeof jQuery == 'undefined') {
console.log('ERROR: NOT LOADED');
}
else{
console.log('OK');
}
</script>
The script 'widget_init.js' should load jQuery if it is not loaded yet.
I have this script 'widget_init.js':
function load_script_jquery(){
if (typeof jQuery == 'undefined') {
var jq = document.createElement('script'); jq.type = 'text/javascript';
jq.src = '/path/to/js/jquery.min.js';
document.getElementsByTagName('head')[0].appendChild(jq);
}
else {
}
}
load_script_jquery();
// some other code
The problem is that it doesn't wait for jQuery to be loaded and it shows error like this:
<script type="text/javascript">
if (typeof jQuery == 'undefined') {
console.log('ERROR: NOT LOADED'); // NOT LOADED
}
else{
console.log('OK'); // NEVER GOES HERE
}
</script>
I tried this also without any effect:
document.write('<script src="/path/to/js/jquery.min.js" type="text/javascript"><\/script>');
How to wait until jQuery is loaded so I can use it ?

Your code to append the jQuery script will be appended after your <script> snippet that checks for it. That's how .appendChild works
The Node.appendChild() method adds a node to the end of the list of children of a specified parent node
Source: https://developer.mozilla.org/en-US/docs/Web/API/Node.appendChild (emphasis mine)
Here are two options to solve this:
If you can insert HTML on the page
You can use this snippet from the HTML5 Boilerplate. It will check if another script has already loaded jQuery, and if not, will load it inline.
<script>window.jQuery || document.write('<script src="js/vendor/jquery-1.11.2.min.js"><\/script>')</script>
Just drop it in your head or body tag before the script that depends on it.
If you need to dynamically load it in the Javascript source
Follow the instructions in this tutorial
(function () {
function loadScript(url, callback) {
var script = document.createElement("script")
script.type = "text/javascript";
if (script.readyState) { //IE
script.onreadystatechange = function () {
if (script.readyState == "loaded" || script.readyState == "complete") {
script.onreadystatechange = null;
callback();
}
};
} else { //Others
script.onload = function () {
callback();
};
}
script.src = url;
document.getElementsByTagName("head")[0].appendChild(script);
}
loadScript("https://ajax.googleapis.com/ajax/libs/jquery/1.6.1/jquery.min.js", function () {
//jQuery loaded
console.log('jquery loaded');
});
})();

You just need callback function, after loading jquery secessfully:
var loadJS = function(url, cb) {
var script_tag = document.createElement('script');
script_tag.setAttribute("type", "text/javascript");
script_tag.setAttribute("src",
url);
if (script_tag.readyState) {
script_tag.onreadystatechange = function() { // For old versions of IE
if (this.readyState == 'complete' || this.readyState == 'loaded') {
cb();//calling callback
}
};
} else { // Other browsers
script_tag.onload = cb;//calling callback function
}
(document.getElementsByTagName("head")[0] || document.documentElement).appendChild(script_tag);
};
And simply call this function with jquery library path and callback function reference:
loadJS(hostUrl + "/js/libraries/jquery.js", callback);

Javascript Dynamic Script Loading IE problems

I'm trying to load dynamically script with this code:
var headID = document.getElementsByTagName("head")[0];
var script = document.createElement('script');
script.type='text/javascript';
script.src="js/ordini/ImmOrd.js";
script.setAttribute("onload", "crtGridRicProd();");
headID.appendChild(script);
I need to launch crtGridRicPrdo() function when the page starts, and in FireFox all works fine but in Internet Explorer I have a problems!

Internet explorer does not support "onload" on script tags, instead it offers the "onreadystatechange" (similarly to an xhr object). You can check its state in this way:
script.onreadystatechange = function () {
if (this.readyState == 'complete' || this.readyState == 'loaded') {
crtGridRicProd();
}
};
otherwise you can call crtGridRicProd() at the end of your js file
EDIT
example:
test.js:
function test() {
alert("hello world");
};
index.html:
<!DOCTYPE html>
<html>
<head>
<title>test</title>
</head>
<body>
<script>
var head = document.getElementsByTagName("head")[0] || document.body;
var script = document.createElement("script");
script.src = "test.js";
script.onreadystatechange = function () {
if (this.readyState == 'complete' || this.readyState == 'loaded') {
test();
}
};
script.onload = function() {
test();
};
head.appendChild(script);
</script>
</body>
you will see the alert in both browser!

I use the following to load scripts one after another (async=false):
var loadScript = function(scriptUrl, afterCallback) {
var firstScriptElement = document.getElementsByTagName('script')[0];
var scriptElement = document.createElement('script');
scriptElement.type = 'text/javascript';
scriptElement.async = false;
scriptElement.src = scriptUrl;
var ieLoadBugFix = function (scriptElement, callback) {
if ( scriptElement.readyState == 'loaded' || scriptElement.readyState == 'complete' ) {
callback();
} else {
setTimeout(function() { ieLoadBugFix(scriptElement, callback); }, 100);
}
}
if ( typeof afterCallback === "function" ) {
if ( typeof scriptElement.addEventListener !== "undefined" ) {
scriptElement.addEventListener("load", afterCallback, false)
} else {
scriptElement.onreadystatechange = function(){
scriptElement.onreadystatechange = null;
ieLoadBugFix(scriptElement, afterCallback);
}
}
}
firstScriptElement.parentNode.insertBefore(scriptElement, firstScriptElement);
}
Use it like this:
loadScript('url/to/the/first/script.js', function() {
loadScript('url/to/the/second/script.js', function() {
// after both scripts are loaded
});
});
One bugfix which the script includes is the latency bug for IE.

You are loading script from external source. So you need to wait until it loads. You can call your function after id completed.
var headID = document.getElementsByTagName("head")[0];
var script = document.createElement('script'); script.type='text/javascript';
script.onload=scriptLoaded;
script.src="js/ordini/ImmOrd.js"; script.setAttribute("onload", "crtGridRicProd();");
headID.appendChild(script);
function scriptLoaded(){
// do your work here
}

When I red your code, I figured out that you try to append an onload event to the script tag.
<html>
<head>
<script type="text/javascript" onLoad="crtGridRicPrdo()">
...
</script>
</head>
<body>
...
</body>
</html>
This will be the result of your javascript code. Why don't you add it to the body tag?
This is the classic way and will defnatly work under IE too. This will also reduce your code:
var bodyID = document.getElementsByTagName("body")[0];
bodyID.setAttribute("onload", "crtGridRicProd();");

For proberly dynamic loading a js-script (or css-file) in IE you must carefully check the path to the loaded file! The path should start from '/' or './'.
Be aware, that IE sometimes loses leading slash - as for instance is described here:
https://olgastattest.blogspot.com/2017/08/javascript-ie.html