I am new to JavaScript. I have a task to write a js script that will be injected to google.com using Chrome DevTools and run on top of it. The script needs to add certain popups on mouseover action - so if I hover over certain elements of the page (such as the Google logo), a certain popup will be shown. The popups all have css stylings.
So far, I have managed to create alerts on mouseover action using EventListener (on google.com). And I have managed to create custom popups with css on my own website. However, I'm having serious trouble combining both.
The problem is essentially: in my own custom website, I put the css bit under "style" tag, and the js script itself under "script" tag. The script than uses the css properties of the popup to create it. However, in Chrome DevTools I'm only able to inject the actual js script (by copy-pasting it the console), and not the css bit.
How should I get around that? Is there a way to add the css within the js, so running the script will lead to the css being added to the "style" section? Is there a different way to inject the script in the DevTools, and separately inject the css and js? Or is there another way to solve this?
Thanks a lot :)
You can do this by creating and running a snippet, to create a snippet:
Open chrome-devtools
Create new snippet (Ctrl+Shift+P, type show snippets, and hit Enter)
document.head.insertAdjacentHTML("beforeend",`<style>
/*Write your css here, sample below*/
body{
color:red !important;
}
</style>`);
// your main script can go here, note, the below code is just a sample
document.body.addEventListener("mouseover", function(){
console.log("logged..")
})
Run the snippet (Ctrl+Enter)
You can also save and use the snippet later, to run the snippet later:
Ctrl+p type ! and the name of your snippet.
The essence of the problem is as follows:
There is a page, I need to modify the contents of the browser extensions, you can use jQuery.
Tried $(document).ready(), but then the contents are still displayed for a short period (FOUC). I can not make changes to the page styles on the server.
I'm using the kango framework to build the extension.
Using only ECMAscript, you can't reliably avoid it. You have like no shot if you wait for DOMContentLoaded event, because at that point the DOM is pretty much rendered and displayed (which is what you see for a short period).
Your best shot would be to modify the CSS as soon as possible. If the stylesheet definition gets loaded before the DOM gets rendered and you would have set like
body {
display: none;
}
you would not see anything. You could try like
<body>
<script>
document.body.style.display = 'none';
</script>
<!-- more html -->
</body>
if that is any viable / useable solution for you.
I suggest you to use a combination of CSS and JavaScript. I had the same issue using jQueryUI on a site I'm building and found that a lot of these solutions out there would make the content unavailable to those without JavaScript.
So, here is what I did:
CSS:
.flash #wrapper {
display: none;
}
This sets <div id="wrapper"> to hidden only if it is a decedent of the flash class. So, to keep it from being hidden from those without JavaScript I add the flash class to <html> element. So, it can only be physically hidden if an end-user has JavaScript enabled, otherwise they'll at least have access via the unstyled content.
JavaScript:
$('html').addClass('flash');
$(document).ready(function() {
/* Do all your stuff */
/* When done show the wrapper with the content styled */
$(#wrapper).show();
});
Depending on your pages time to load you might get a little flash, but it won't be a flash of unstyled content, which is rather ugly. In my case I had a jQueryUI menu item that would flash the normal <ul> element first then the menuUI item, and my <div> elements are resized with jQuery so that each <div> column is equal height, but it would flash the different heights first. This fixed it while still giving accessibility to non-JavaScript browsers.
Twitter generates me box code to insert on page: http://pastebin.com/5TgkL5vP but on slow connection it prevent page from loading. Is there any way to add "Loading..." and make it async? (I know about iframe but its awful way)
There is a solution in here;
http://od-eon.com/blogs/stefan/asynchronous-loading-twitter-widgets/
$(window).load(function(){
$.getScript('http://widgets.twimg.com/j/2/widget.js', function(){
$.getScript('/media/js/twitter.js', function(){
$('#twtr-widget-1').appendTo('#twitter_p')
})
})
})
To delay the loading of the twitter widget you could load it after your whole page is loaded. You could use the window's onload event handler to start loading the twitter widget once your page has been downloaded.
Or you could use a javascript library (like jquery) to run that code once you HTML is loaded but images and CSS and other assets are still loading: jquery's .ready() method does just that.
In case you don't want to use bare javascript (although recommended for learning) jquery (like others) does provide a .load() event that behaves just like the onload example on W3c.
In any case, with any of those two methods you could place a "loading..." text in a placeholder and then replace it with the widget once it's loaded.
You should try experimenting with both and see which one produces the best perceived results. Sometimes you want the page's content to load blazingly fast, in that case you should hold all external content from being loaded until the content is loaded (using onload or .load()), while sometimes you want everything to be loaded more or less at the same time (using .ready()).
I hope it didn't come out backwards :D.
The solution explain by od-eon.com is OK but for IE the CSS is not correctly added because it tries to add CSS in a window onload event. This event is fired asynchronously so no CSS is added.
The line $('#twtr-widget-1').appendTo('#twitter_p') is not useful.
You must not add a CSS position attribute to the div which will contain the box because nothing is displayed in this case. If you want to add this box in an absolute div you must add an empty div in it and pass the div's id in parameter.
When adding JQuery to hide a class it of course waits for the page to load then hides the class, same thing for 'addClass'. There has got to be a better or faster way for it to 'load' as the page is loading. Anyone know of any ideas? I have given my sites JQuery scripts below with links to see them in action:
Hides sub filters: Link to example of my script to hide sub filters (notice left navigation filters)
if(jQuery('.refinement_category_section').length){
jQuery('.refinement_custom_category_section').hide() &&
jQuery('.refinement_filter').hide();
}
jQuery(document).ready(function(){
if(jQuery('.refinement_category_section').length){
jQuery('.refinement_custom_category_section').hide() &&
jQuery('.refinement_filter').hide();
}
});
OR
Adds a Class:Link to example of my script adding Class (notice left navigation filters)
$('.refinement_brand_section').parent().addClass('filterresults');
Using Firebug, it appears that the issue is with the number of images that you are loading. My suggestion is to dynamically load pictures for your items using javascript after applying your style changes or have a smaller number of items on the page (or both). This will result in a degraded, but still functional interface for non-javascript users. For javascript-enabled browsers, you can adjust how and how many images are loaded to still achieve a nice effect.
You should also use sprites for your small interface elements so that you're downloading a single image and using CSS to display various portions of it. Combining your javascript files and stylesheets for your production site would also help quite a bit -- you've got 20+ js files and 13+ stylesheets, each of which requires a separate request. You might want to run YSlow and follow it's other recommendations.
you can add CSS rules to hide these classes and then change it after jquery loads
.refinement_category_section, .refinement_custom_category_section, .refinement_filter {
display: none;
}
I found some good cons here:
The noscript element only detects whether the browser has JavaScript enabled or not. If JavaScript is disabled in the Firewall rather than in the browser then the JavaScript will not run and the content of the noscript element will not be displayed.
Many scripts are dependent on a specific feature or features of the language being supported in order for them to be able to run (for example document.getElementById). Where the required features are not supported the JavaScript is unable to run but since JavaScript itself is supported the noscript content will not be displayed.
The most useful place to use the noscript element is in the head of the page where it would be able to selectively determine what stylesheet and meta elements get applied to the page as the page is loading rather than having to wait until the page is loaded. Unfortunately the noscript element is only valid within the body of the page and so cannot be used in the head.
The noscript element is a block level element and therefore can only be used to display entire blocks of content when JavaScript is disabled. It cannot be used inline.
Ideally, web pages should use HTML for the content, CSS for the appearance, and JavaScript for the behavior. Using the noscript element is applying a behavior from within the HTML rather than applying it from JavaScript.
Source: http://javascript.about.com/od/reference/a/noscriptnomore.htm
I very much agree on last point. Is there a way to make and add an external <noscript> file? Should we place <noscript> in the <head>?
It's better to have the default be non-javascript, and then let a javascript code overwrite with a javascript enabled page. Doesn't have to be much. Can just be a display:none; block, which is then set to display:block; by javascript, and vice versa for the non-js page.
After pondering for many days and changing my code back and forth, I think I have clearer picture now and would like to share my two cents worth on the subject before I forget.
<div id='noscript'>show non-js content</div>
<script>document.getElementById('noscript').style.display='none';</script>
<script id='required script'>show js content</script>
vs
<noscript>show non-js content</noscript>
<script id='required script'>//show js content</script>
Depending on the situation, there are three cases for consideration:
Case 1 - If required script is inline
JavaScript disabled
Content in <noscript> element appears immediately, non-js content is
shown
Content in <div> element appears immediately, non-js content is shown
JavaScript enabled
Content in <noscript> element does not appear at all, js content shown
Content in <div> element may momentarily appear before being hidden, js
content shown
For this case, using <noscript> element is advantageous.
Case 2 - If required script is from external (third-party) source, but hiding of <div> element is done with inline script
JavaScript disabled
Content in <noscript> element appears immediately, non-js content is
shown
Content in <div> element appears immediately, non-js content is shown
JavaScript enabled but required script is blocked
Content in <noscript> element does not appear at all, nothing is shown!
Content in <div> element may momentarily appear before being hidden, nothing is shown!
JavaScript enabled and required script is received
Content in <noscript> element does not appear at all, js content shown
Content in <div> element may momentarily appear before being hidden, js
content shown
For this case, using <noscript> element is advantageous.
Case 3 - If required script hides the <div> element
JavaScript disabled
Content in <noscript> element appears immediately, non-js content is
shown
Content in <div> element appears immediately, non-js content is shown
JavaScript enabled but required script is blocked
Content in <noscript> element does not appear at all, nothing is shown!
Content in <div> element appears, non-js content is shown
JavaScript enabled and required script is received
Content in <noscript> element does not appear at all, js content shown
Content in <div> element may momentarily appear before being hidden, js
content shown
For this case, using <div> element is advantageous.
In summary
Use <noscript> element if rendering of the HTML content depends on third-party scripts or if the required script is inline. Else, use <div> element and make sure that the required script contains:
document.getElementById('noscript').style.display='none';
Although Tor Valamo has an elegant answer to this problem, there is an issue which may cause you to opt out of using this technique.
The problem is (usually) IE. It has the tendency to load and execute the JS a bit slower than other browsers causing it to sometimes flash the "Please Enable Your Javascript" div for a split second before it then loads the JS and hides the div.
It is annoying and to get around this you can implement the "classic". <noscript> redirect approach.
<head>
<noscript><meta http-equiv="refresh" content="0; URL=/NO_SCRIPT_URL/ROUTE_HERE"/></noscript>
</head>
This is the most solid technique that I've come across with regards to this little nasty.
One useful application for noscript that I've seen is for a progressively-enhanced async loading of heavy content (especially "below the fold"). Big images, iframes, etc. can be wrapped in noscript in the HTML source, and then the unwrapped elements can be appended to the page using JavaScript after the DOM is ready. This unblocks the page and can make for a much quicker initial loading experience, especially if your interface relies on JS/JQ interactions applied after the document is ready (2 seconds vs. 6 seconds for a portfolio page I consulted on).
These days it seems almost every browser runs Javascript, but you can never know who is going to be accessing your site. These days even screen readers and web crawlers use Javascript, and sometimes make AJAX requests if they have to.
That said, if you're going to fall back to no-Javascript, there is a much better way than a <noscript> tag. Simply do this in the HEAD of your document:
<script type="text/javascript">
document.getElementsByTagName('html')[0].className += ' Q_js'; // better than noscript
</script>
With this technique, you can easily refer to the Q_js class in your CSS to hide things. With the <noscript> tag, the best you can hope for is to include an additional CSS file to override previous CSS. This becomes important when some elements with static content are supposed to be hidden right away (not flicker) until Javascript can make them more dynamic.
In short, the technique I suggested addresses all your cons 1-5, and I believe it's strictly better than using <noscript>.
In the (hopefully near) future you will be able to use css #media scripting:
#media (scripting: none) {
/* styles for when JS is disabled */
}
I create a full height, full width, position:fixed div in all pages with some id .
<div id='noscript_div' style='position:fixed;z-index:20000000;height:100%;width:100%;line-height:100%;'>enable JS buddy</div>
$('#noscript_div').hide();
$(document).ready(function(event){
});
I am not an expert . This worked for me .
I am sorry but, this case will suit only if you want the user to have his javascript enabled always
the simple ideea is in this times your website may adapt to no javascript usage on slow devices using noscript tag like an entity for the entire content of your website**(your html should be prepared to no javascript and all controls must work also if javascript is off,users using basic html controls shoul be able to do everything they done before when javascript was active.So <noscript></noscript> can be the dynamic switch to the same content in other way with the same results=solving the problem wich is the reason the users open your url).**You can see is no matter javascript is or not present ,the website's functionality can be "the same" in any cases js enabled / disabled.On chinese slow devices eg:Samsung neo mini phone this method can run an website without any delays on low internet traffic..
try to run this auto double functionallity website if js is on/off cases:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"><HTML>
<HEAD>
<TITLE>noscript can change the Internet forever</TITLE>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.3/jquery.min.js"></script>
</HEAD>
<BODY>
<SCRIPT LANGUAGE="JavaScript">
<!--
$(document).ready(function(){
$('noscript').replaceWith(function() {
return this.textContent || this.innerText;
});
$("p#javascripton").css("background-color", "yellow");
$("p").click(function(){
$(this).hide();
});
});
//-->
</SCRIPT>
<noscript>
<p>
Noscript's usage today can be logical for <p id="javascripton">eg pc/laptop/high quality tablets usage the complete website with all features:images high resolution,javascript<br><h1>OR without javascript so no high resolutions images inserted with a jquery automated script generated from some php+javascript scripts so have usage for 80% mobile application cause almost are from China ,so low quality products=low cpu,low ram :IN THIS CASE SOMEONE CAN THINK TO SWITCH HIS PHONE TO NO JAVASCRIPT USAGE SO IF ANY PROGRAMMER CAN ADAPT AN ENTIRELY APPLICATION TO THE METHOD I USED IN THIS EXAMPLE AUTOMATED HIS BROWSER IS ADAPT FOR ANY RANDOM ACTION ABOUT THE USER CHOISE(YOU UNDERSTAND "TO USE OR NOT JAVASCRIPT") SO HIS CHINESE PHONE CAN BE APROXIMATELLY APROACH LIKE QUALITY OF SPEED EXECUTION THE OTHERS PC/LAPTOPS/TABLETS QUALITY PRODUCTS.<BR><BR>This stupid example is the best example how no script tag can change the quality of services on this planet ,boost the speed of the internet connection and stops unnecessary use of A LOT OF INTERNET TRAFFIC on slow devices..a simple tag can change the entirely dynamic of programmer's views so entirely Planet's beneficts</h1><p> <br>
run this code in two instances :<br>with browser javascript enable <br>and without(browser's javascript disable or eg a firefox plugin noscript states on/off)
</p>
</noscript>
</BODY></HTML>
and to say more on this .. right noscript was invented to work like a trigger when js is disabled but you can work around this feature to change the course of internet functionality about how is now ,to change it's dynamics....
Like all things, use the right tool for the job.
If you are using Google Maps API, you have a static image via tag and that gets replaced with dynamic JS map. Google have recently started charging for everything thus with the above example it's going to cost you twice, once for static and once for dynamic. The static map is only relevant if JS is disabled. Therefore to save double paying it seems to me the best solution is to wrap the tag for the static map in a tag.