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Lazy-load a javascript script?

Is there a way I can wrap an external JS script embed with lazy-load behavior to only execute when the embed is in the viewport?
Context: I have an external javascript embed that when run, generates an iframe with a scheduling widget. Works pretty well, except that when the script executes, it steals focus and scrolls you down to the widget when it’s done executing. The vendor has been looking at a fix for a couple weeks, but it’s messing up my pages. I otherwise like the vendor.
Javascript embed call:
<a href=https://10to8.com/book/zgdmlguizqqyrsxvzo/ id="TTE-871dab0c-4011-4293-bee3-7aabab857cfd" target="_blank">See
Online Booking Page</a>
<script src=https://d3saea0ftg7bjt.cloudfront.net/embed/js/embed.min.js> </script> <script>
window.TTE.init({
targetDivId: "TTE-871dab0c-4011-4293-bee3-7aabab857cfd",
uuid: "871dab0c-4011-4293-bee3-7aabab857cfd",
service: 1158717
});
</script>
While I'm waiting for the vendor to fix their js, I wondered if lazy-loading the JS embed may practically eliminate the poor user experience. Warning: I'm a JS/webdev noob, so probably can't do anything complicated. A timer-based workaround is not ideal because users may still be looking at other parts of the page when the timer runs out. Here are the things I’ve tried and what happens:
I tried:
What happened:
Add async to one or both of the script declarations above
Either only shows the link or keeps stealing focus.
Adding type=”module” to one or both script declarations above
Only rendered the link.
Wrapping the above code in an iframe with the appropriate lazy-loading tags
When I tried, it rendered a blank space.
Also, I realize it's basically the same question as this, but it didn't get any workable answers.

I actually also speak french but I'll reply in english for everybody.
Your question was quite interesting because I also wanted to try out some lazy loading so I had a play on Codepen with your example (using your booking id).
I used the appear.js library because I didn't really want to spend time trying some other APIs (perhaps lighter so to take in consideration).
The main JS part I wrote is like this:
// The code to init the appear.js lib and add our logic for the booking links.
(function(){
// Perhaps these constants could be put in the generated HTML. I don't really know
// where they come from but they seem to be related to an account.
const VENDOR_LIB_SRC = "https://d3saea0ftg7bjt.cloudfront.net/embed/js/embed.min.js";
const UUID = "871dab0c-4011-4293-bee3-7aabab857cfd";
const SERVICE = 1158717;
let vendorLibLoaded = false; // Just to avoid loading several times the vendor's lib.
appear({
elements: function() {
return document.querySelectorAll('a.booking-link');
},
appear: function(bookingLink) {
console.log('booking link is visible', bookingLink);
/**
* A function which we'll be able to execute once the vendor's
* script has been loaded or later when we see other booking links
* in the page.
*/
function initBookingLink(bookingLink) {
window.TTE.init({
targetDivId: bookingLink.getAttribute('id'),
uuid: UUID,
service: SERVICE
});
}
if (!vendorLibLoaded) {
// Load the vendor's JS and once it's loaded then init the link.
let script = document.createElement('script');
script.onload = function() {
vendorLibLoaded = true;
initBookingLink(bookingLink);
};
script.src = VENDOR_LIB_SRC;
document.head.appendChild(script);
} else {
initBookingLink(bookingLink);
}
},
reappear: false
});
})();
I let you try my codepen here: https://codepen.io/patacra/pen/gOmaKev?editors=1111
Tell me when to delete it if it contains sensitive data!
Kind regards,
Patrick

This method will Lazy Load HTML Elements only when it is visible to User, If the Element is not scrolled into viewport it will not be loaded, it works like Lazy Loading an Image.
Add LazyHTML script to Head.
<script async src="https://cdn.jsdelivr.net/npm/lazyhtml#1.0.0/dist/lazyhtml.min.js" crossorigin="anonymous" debug></script>
Wrap Element in LazyHTML Wrapper.
<div class="lazyhtml" data-lazyhtml onvisible>
<script type="text/lazyhtml">
<!--
<a href=https://10to8.com/book/zgdmlguizqqyrsxvzo/ id="TTE-871dab0c-4011-4293-bee3-7aabab857cfd" target="_blank">See
Online Booking Page</a>
<script src=https://d3saea0ftg7bjt.cloudfront.net/embed/js/embed.min.js>
</script>
<script>
window.TTE.init({
targetDivId: "TTE-871dab0c-4011-4293-bee3-7aabab857cfd",
uuid: "871dab0c-4011-4293-bee3-7aabab857cfd",
service: 1158717
});
</script>
-->
</script>
</div>

Removing a script tag with a specific content using jquery

I have a page that i dont have access to its an obvius site. I would like to remove a script html tag with a content. For now i have this but is not working. I am using userscripts like coding!
function main(){
var def = $('script[type="text/javascript"]').html();
$('script[type="text/javascript"]').each(function() {
if (def == 'document.write("<scr"+"ipt type=\'text/javascript\' src=\'http://storing.com/javascripts/"+(new Date()).getTime()+"/3e155555e1b26c2d1ced0f645e_1_1.js\'></scr"+"ipt>")')
$('script[type="text/javascript"]').remove();
}
}
UPDATE:
<script type="text/javascript">document.write("<scr"+"ipt type='text/javascript' src='http://somedomain.com/javascripts/"+(new Date()).getTime()+"/3e1a0cd37f25a6e1b26c2d1ced0f645e_1_1.js'></scr"+"ipt>")</script>
This is the whole script what i want to remove... it inserts a div that i am removing right now i just wanted to know if there is any other method. BUt as i see the only is the hosts file thing :)

I don't believe this will work, since a loaded script will already have run.
That said, you probably want something like this:
$('script').each(function() {
if (this.src.substring(0, 31) === 'http://storing.com/javascripts/') {
$(this).remove();
}
});
It's impossible to match the <script> tag based on the output of .html() because that only returns the contents of the element, and not the outer <script> element nor the element's attributes.

When a script is loaded in a page, it is evaluated and executed by the browser immediately after. After the script has been executed, the content of the script tag is irrelevant.
You might be able to achieve what you want by unbinding the events which might have been loaded by the script. Are there any events you want to disable?
If the script is in a certain domain and you want to block all traffic to it, you could add the following entry to your hosts file:
127.0.0.1 storing.com
This will prevent the request to reach it's destination.

how to synchronize web site content while loading page

I want to synchronize web site like when page load first it will load content then images then flash content then another content.
Like i have seen the same at http://gmailblog.blogspot.com/ [ see how images load ]
Is there any way to achieve? Any link or source code would be appreciated.

I seen the web site. This is the same thing that happens with bing. How to do this ?
In the core HTML code give the <img src="loading.gif" id="1"/> or whatever element you want.
When the Core HTML is done, before the </body> tag, use javascript to change the
attributes values (for eg. "src" attribute of the img element). Remeber the javascript need to be written at the end of the HTML before closing the body tag. The browser will load the
contents accordingly in sequence. This can be used to achieve priority based loading of HTML components.

You can synchronize loading of all elements on your page by controlling it using JS. For ex: one strategy to load images after content would be:
a) In your html, instead of in the src attribute, specify the image location in another attribute, say 'isrc'.
b) Inside your onload callback (assumes you're using jQuery):
var loadCounter = 0;
$('img').each(function() {
if($(this).attr('isrc')) {
this.onload = function() {
loadCounter++;
if($('img[isrc]').length == loadCounter) {
// .. proceed to loading other stuff like flash etc..
}
}
$(this).attr('src', $(this).attr('isrc')); // load the image
}
});

Trying to load an API and a JS file dynamically

I am trying to load Skyscanner API dynamically but it doesn't seem to work. I tried every possible way I could think of and all it happens the content disappears.
I tried console.log which gives no results; I tried elements from chrome's developers tools and while all the content's css remains the same, still the content disappears (I thought it could be adding display:none on the html/body sort of). I tried all Google's asynch tricks, yet again blank page. I tried all js plugins for async loading with still the same results.
Skyscanner's API documentation is poor and while they offer a callback it doesn't work the way google's API's callback do.
Example: http://jsfiddle.net/7TWYC/
Example with loading API in head section: http://jsfiddle.net/s2HkR/
So how can I load the api on button click or async? Without the file being in the HEAD section. If there is a way to prevent the document.write to make the page blank or any other way. I wouldn't mind using plain js, jQuery or PHP.
EDIT:
I've set a bounty to 250 ontop of the 50 I had previously.
Orlando Leite answered a really close idea on how to make this asynch api load although some features doesn't work such as selecting dates and I am not able to set styling.
I am looking for an answer of which I will be able to use all the features so that it works as it would work if it was loading on load.
Here is the updated fiddle by Orlando: http://jsfiddle.net/cxysA/12/
-
EDIT 2 ON Gijs ANSWER:
Gijs mentioned two links onto overwriting document.write. That sounds an awesome idea but I think it is not possible to accomplish what I am trying.
I used John's Resig way to prevent document.write of which can be found here: http://ejohn.org/blog/xhtml-documentwrite-and-adsense/
When I used this method, I load the API successfuly but the snippets.js file is not loading at all.
Fiddle: http://jsfiddle.net/9HX7N/

I belive what you want is it:
function loadSkyscanner()
{
function loaded()
{
t.skyscanner.load('snippets', '1', {'nocss' : true});
var snippet = new t.skyscanner.snippets.SearchPanelControl();
snippet.setCurrency('GBP');
snippet.setDeparture('uk');
snippet.draw(document.getElementById('snippet_searchpanel'));
}
var t = document.getElementById('sky_loader').contentWindow;
var head = t.document.getElementsByTagName('head')[0];
var script = document.createElement('script');
script.type = 'text/javascript';
script.onreadystatechange= function() {
if(this.readyState == 'complete') loaded();
}
script.onload= loaded;
script.src= 'http://api.skyscanner.net/api.ashx?key=PUT_HERE_YOUR_SKYSCANNER_API_KEY';
head.appendChild(script);
}
$("button").click(function(e)
{
loadSkyscanner();
});
It's load skyscanner in iframe#sky_loader, after call loaded function to create the SearchPanelControl. But in the end, snippet draws in the main document. It's really a bizarre workaround, but it works.
The only restriction is, you need a iframe. But you can hide it using display:none.
A working example
EDIT
Sorry guy, I didn't see it. Now we can see how awful is skyscanner API. It puts two divs to make the autocomplete, but not relative to the element you call to draw, but the document.
When a script is loaded in a iframe, document is the iframe document.
There is a solution, but I don't recommend, is really a workaround:
function loadSkyscanner()
{
var t;
this.skyscanner;
var iframe = $("<iframe id=\"sky_loader\" src=\"http://fiddle.jshell.net/orlleite/2TqDu/6/show/\"></iframe>");
function realWorkaround()
{
var tbody = t.document.getElementsByTagName("body")[0];
var body = document.getElementsByTagName("body")[0];
while( tbody.children.length != 0 )
{
var temp = tbody.children[0];
tbody.removeChild( temp );
body.appendChild( temp );
}
}
function snippetLoaded()
{
skyscanner = t.skyscanner;
var snippet = new skyscanner.snippets.SearchPanelControl();
snippet.setCurrency('GBP');
snippet.setDeparture('uk');
snippet.draw(document.getElementById('snippet_searchpanel'));
setTimeout( realWorkaround, 2000 );
}
var loaded = function()
{
console.log( "loaded" );
t = document.getElementById('sky_loader').contentWindow;
t.onLoadSnippets( snippetLoaded );
}
$("body").append(iframe);
iframe.load(loaded);
}
$("button").click(function(e)
{
loadSkyscanner();
});
Load a iframe with another html who loads and callback when the snippet is loaded. After loaded create the snippet where you want and after set a timeout because we can't know when the SearchPanelControl is loaded. This realWorkaround move the autocomplete divs to the main document.
You can see a work example here
The iframe loaded is this
EDIT
Fixed the bug you found and updated the link.
the for loop has gone and added a while, works better now.
while( tbody.children.length != 0 )
{
var temp = tbody.children[0];
tbody.removeChild( temp );
body.appendChild( temp );
}

For problematic cases like this, you can just overwrite document.write. Hacky as hell, but it works and you get to decide where all the content goes. See eg. this blogpost by John Resig. This ignores IE, but with a bit of work the trick works in IE as well, see eg. this blogpost.
So, I'd suggest overwriting document.write with your own function, batch up the output where necessary, and put it where you like (eg. in a div at the bottom of your <body>'). That should prevent the script from nuking your page's content.
Edit: OK, so I had/took some time to look into this script. For future reference, use something like http://jsbeautifier.org/ to investigate third-party scripts. Much easier to read that way. Fortunately, there is barely any obfuscation/minification at all, and so you have a supplement for their API documentation (which I was unable to find, by the way -- I only found 'code wizards', which I had no interest in).
Here's an almost-working example: http://jsfiddle.net/a8q2s/1/
Here's the steps I took:
override document.write. This needs to happen before you load the initial script. Your replacement function should append their string of code into the DOM. Don't call the old document.write, that'll just get you errors and won't do what you want anyway. In this case you're lucky because all the content is in a single document.write call (check the source of the initial script). If this weren't the case, you'd have to batch everything up until the HTML they'd given you was valid and/or you were sure there was nothing else coming.
load the initial script on the button click with jQuery's $.getScript or equivalent. Pass a callback function (I used a named function reference for clarity, but you can inline it if you prefer).
Tell Skyscanner to load the module.
Edit #2: Hah, they have an API (skyscanner.loadAndWait) for getting a callback once their script has loaded. Using that works:
http://jsfiddle.net/a8q2s/3/
(note: this still seems to use a timeout loop internally)

In the skyrunner.js file they are using document.write to make the page blank on load call back... So here are some consequences in your scenario..
This is making page blank when you click on button.
So, it removes everything from page even 'jQuery.js' that is why call back is not working.. i.e main function is cannot be invoked as this is written using jQuery.
And you have missed a target 'div' tag with id = map(according to the code). Actually this is the target where map loads.
Another thing i have observed is maps is not actually a div in current context, that is maps api to load.
Here you must go with the Old school approach, That is.. You should include your skyrunner.js file at the top of the head content.
So try downloading that file and include in head tag.
Thanks

load specific image before anything else

I'm a creating a loading screen for website I am making. The website loads many images, scripts, etc. The HTML and CSS part is great, but I need a way to guarantee that the "loading..." image will be loaded before anything else.
I'm using jQuery, and everything is initiated within $(function () { ... });. I imagine that the code for this would need to be called before/outside that block, and the code to remove the loading screen will be called at the very end of that block. Currently, the loading image is set as a DIV background, which is the way I prefer it. However, if it's completely necessary, I will settle for an IMG tag.
Update: (solution)
I was able to answer my own question by using a combination of Robin and Vlad's responses. Both were very good, and excellent answers, however the problem is that they were aimed to load an image before another image, rather than load an image before anything else. (CSS, JS, etc...)
Here's the dirty version of what I came up with:
var files = [new Image(), document.createElement('link'), document.createElement('script')];
files[0].setAttribute('src', 'images/loading.gif');
files[1].setAttribute('rel', 'stylesheet');
files[1].setAttribute('type', 'text/css');
files[1].setAttribute('href', 'test.css');
files[2].setAttribute('type', 'text/javascript');
files[2].setAttribute('src', 'js/jquery-1.5.1.min.js');
window.onload = function (e) {
document.getElementsByTagName('head')[0].appendChild(files[1]);
document.getElementsByTagName('head')[0].appendChild(files[2]);
}
Taking a look at the load sequence on the network tab of Chrome's developer console shows that 'loading.gif' is loaded first, then 4 dummy images, then 'test.css', and then 'jquery.1.5.1.min.js'. The CSS and JS files don't begin to load, until they've been inserted into the head tag. This is exactly what I want.
I'm predicting that I may begin to have some problems, however, when I begin to load a list of files. Chrome reports that sometimes the JS file is loaded first, but the majority of the time the CSS file is loaded first. This isn't a problem, except when I begin to add files to load, I will need to ensure that jQuery is loaded before a script file that uses jQuery.
If anyone has a solution for this, or a way to detect when the CSS/JS files are finished loading, using this method, then please comment. Though, I'm not sure that it's going to be a problem yet. I may need to ask a new question in the future about this, if I start to run into problems.
Thank you to every who has helped with this issue.
Update: (glitch fix)
I ended up running into a lot of problem with this method, because the script files were being loaded asynchronously. If I would clear the browser cache, and then load the page, it would finish loading my jquery dependent files first. Then if I refreshed the page, it would work, because jquery was loaded from cache. I solved this by setting up an array of files to load, then putting the load script into a function. Then I would step through each array item using this code:
element.onload = function() {
++i; _step();
}
element.onreadystatechange = function() {
if (("loaded" === element.readyState || "complete" === element.readyState)) { ++i; _step(); }
}

You can reuse resource prealoding browser support.
I'm not sure it works across all browsers but in my case this approach helps me to load images first. Also it allows to define concrete images so UI specific could be skipped
First define in header what resource you want to preload and define resource priority
<link rel="preload" href="link-to-image" as="image">
or
<link rel="preload" href="link-to-image">
Second line allow to increase loading priority across all object types (scripts / images / styles). First line - only through images.
Then define in body link to image as usual:
<img src="link-to-image" alt="">
Here is my working example
https://jsfiddle.net/vadimb/05scfL58/

As long as the "loading..." image is positioned before any other html elements, it should load first. This of course depends on the size of the image. You could put the loading div right after the tag and position it using 'position:absolute'.
Regarding the code to remove the loading screen, one method is to do the following.
Put all the images, scripts that need to be loaded in a hidden div (display: none)
Set up a variable that will hold the total of the images / scripts to be loaded
Set up a counter variable
Attach to each image / script the "onload" event
Everytime the "onload" event is triggered it will call a function that will increment the counter variable and check if the value of the counter equals the value of the total variable
If all resources have been loaded, fire a custom event that will show the div with the images, and hide the div with the loading screen.
The code below isn't tested so it might not work. Hope it helps
var totalImages = 0;
var loadCounter = 0;
function incrementLoadCounter() {
loadCounter++;
if(loadCounter === totalImages) {
$(document).trigger('everythingLoaded');
}
}
function hideLoadingScreen() {
$('#loadingScreen').hide();
$('#divWithImages').show();
}
$(document).ready(function(e) {
$('#loadingScreen').bind('everythingLoaded', function(e) {
hideLoadingScreen();
});
var imagesToLoad = $('img.toLoad');
totalImages = imagesToLoad.length;
$.each(imagesToLoad, function(i, item) {
$(item).load(function(e) {
incrementLoadCounter();
})
});
})

I'm not sure if it's possible to enforce.
If it is, try adding this in the head-tag:
<script type="text/javascript">
if(document.images)
(new Image()).src="http://www.image.com/example.png";
</script>
In theory that may load and cache that image before anything else.

I think if you place the IMG tag at the top of your html body it will be loaded first. If you do not want to move your div just use a copy of the image tag. Once the images is loaded it will be shown in every image tag which shows the same picture.

Or you could use spin.js as loading image. It display this "loading cycle image" via javascript.
Check it out under:
http://fgnass.github.com/spin.js/