When loading a script on an HTML page, you need to be careful not to harm the loading performance of the page. As I told you earlier, when the parser finds this line, it goes to fetch the script and executes it. This is bad because there is a lot of delay introduced. In doing so, the script is loaded and executed after all the page is already parsed and loaded, which is a huge improvement over the head alternative. This is the best thing you can do if you need to support older browsers that do not support two relatively recent features of HTML: async and defer.
For the support table, check caniuse. These attributes only make sense when using the script in the head portion of the page, and they are useless if you put the script in the body footer like we saw above.
The parsing is paused until the script is fetched, and executed. Once this is done, parsing resumes. The parsing is done without any pauses, and when it finishes, the script is fetched, and executed. Parsing is done before the script is even downloaded, so the page appears to the user way before the previous example.
Parsing finishes just like when we put the script at the end of the body tag, but overall the script execution finishes well before, because the script has been downloaded in parallel with the HTML parsing.
Neither async nor defer guarantee anything on blocking rendering. This is up to you and your script for example, making sure your scripts run after the onLoad event.
Once this is done, the browser will emit the domComplete event, and then onLoad. See the MDN for more. Another case pro defer : scripts marked async are executed in casual order, when they become available. Scripts marked defer are executed after parsing completes in the order which they are defined in the markup. The best thing to do to speed up your page loading when using scripts is to put them in the headand add a defer attribute to your script tag:.
I prepare all this information in my HTML which will be displayed as a kind of popup. I just toggle the visibility of by popup div from hidden to visible. To set the position of my popup div, I have to calculate depending on the height of the image.
So, I have to wait for the image to load to know its dimension before setting position and switching visibility to visible.
Note that it's important to do it in the order above: First attach the handler, then set the src. If you do it the other way around, and the image is in cache, you may miss the event.
The callbacks wouldn't happen between the lines if they were registered, they'd wait in the queue, but if there aren't any, the event isn't required to wait.
If you use jQuery, you can use its load event. Here is the solution that works perfectly fine to wait for an image to load first and then load another image don't forget to display a "please wait! Either the Internet speed is slow or fast, and the browser will wait for the whole page to load with all the images even if they are linked externally and then execute the function, so the second image is displayed only after the first image loads fine.
Active 7 months ago. Viewed 89k times.Images are critical. Whether it is marketing banners, product images or logos, it is impossible to imagine a website without images. Sadly though, images are often heavy files making them the single biggest contributor to the page bloat. Instead, we need to make our web pages load really fast with them.
Before we dive right in, here is a sample video that demonstrates the concept. In short, a gray placeholder box is rendered on the page until it scrolls into view—at which point the actual image loads in place of the box. Similarly, lazy loading defers the loading of resources on the page as long as they are not needed.
Same deal for an image—load it when we need it.Ghost recon 2 [archivio]
If the user never scrolls to the point of the page that contains the image, then the user will never see that image. It also never loads in the first place because, hey, it was never needed.
You may already start to see how this benefits both you and the user. Here are two of the advantages we get with lazy loading. The obvious benefit is that we get smaller web pages that load faster. Lazy loading reduces the number of images that need to be loaded on a page up front. Fewer image requests mean fewer bytes to download. And fewer bytes to download means the page renders faster than if those bytes and requests were being made.
This ensures that any device on any network is able to download and process the remaining resources much faster. Hence, the time from request to render becomes smaller and the page becomes usable much earlier.
The second benefit is for you as a website administrator.I recently launched a CSS animation course for designers and developers wanting to improve their web animation skills. While building the course, I ran into the issue where content would animate before assets had downloaded.
This article covers the approach I put together to fix the problem and ensure all animations played when expected. For example, we want to fade in a hero header on load, so we add the fade-in keyframes, setting up the animation, but then the animations starts before the background image is downloaded. We get a half-loaded image fading in, and even worse, our logo or headline appear before the background is ready. When we load a website, the browser tries to make things are fast as possible by downloading and rendering the HTML and CSS while downloading other assets such as images in parallel.
This approach waits for all assets on a page to load. You might want to only wait for one image, in your header for example. Thankfully there are load events for each image. The animation-play-state property is well supported by modern browsers. It tells the browser whether the current animation is running or paused.
We add this to our CSS. It will make sure it applies to all of the :before and :after pseudo-elements also.Karmic number 16
All this does is look at all the images on the page and once they are all loaded, it fires the allImagesLoaded function which simply prints a message to the console. In reality, we can't be sure this is always going to be the case.Wife ne apna salva banaya
To do so, we're going to clone every image behind the scenes i. Here's what the new script might look like:. There's a lot going on in this line, so let's break it down.
We could also write this one-liner like this:.
We add an event listener to this generic image element before adding its source. That way we can be certain the load event listener will capture the load event.
And note that most browsers will cache image downloads, so this doesn't actually result in downloading the image twice, like you may think. But even if the image has been downloaded and cached already, the load event listener will still fire appropriately. Thus, this is the safer way to ensure all images have been downloaded, and then you can do whatever you want with them. Note that this example was based on all images on a page. That's certainly not something you need to do. You could scope the images you're targeting to be more specific if you only need to know when images within a certain scope or context have been loaded.
At least I'm pretty sure that's what is happening because the script will work fine with the images precached for example if I refresh after loading the page previously.
Making Animations Wait
Active 5 years, 2 months ago. Viewed 23k times. Braains Braains 1 1 gold badge 4 4 silver badges 21 21 bronze badges. This question still gets views 4 years later so I thought I mention that if you have a lot of images you may want to call the recursive loadImages with setTimeout Active Oldest Votes.
Maybe this will help: currentimage. Neptilo 1 1 gold badge 4 4 silver badges 16 16 bronze badges. I was looking at this but my understanding is that the rest of the script will continue to run until the image loads and that function is triggered, and so I'll have the same race condition. Braains, If properly implemented, then no.
Wolff Jun 4 '13 at Give me a few minutes here to implement this and see if it works! Wolff A. Wolff Could you maybe explain a little of what is happening in your example code?
I'm not as familiar with JQuery as I should be. This is to avoid any race condition. You will start loading next image only when previous as fully loaded. After I try implementing the other answer I will try this. I'm a little more familiar with recursion than JQuery so I want to try that first. Good Luck! Tried that, but I'm not just loading one image, I'm loading an image each time through the loop. All of this happens after the page loads.
The problem with preloading is that I'm dealing with a potentially large number of images. Sign up or log in Sign up using Google.
You can also run a function when an image fails to load using the onerror event. The process is to define the function to run when the image is loaded, the function to run when the image fails to load, then you set the source path to the image. A good example where you can make use of those events is if you are creating a photo gallery. When you select an image, you can add a the words "Loading" while the images are loading in the background.
Only when the image is loaded you show it to the user. Did you like this article? You can subscribe to read more awesome ones. Sam Feb 7 :. Sam Yes, you can still make use of it.
In fact, the same method should work in future browsers as long as we use the image tag for images. Anonymous Oct 30 :. Ibrahim Oct 30 :. Kingsam Perry Andrew May 26 :. Nice article.Aksha chamudi sinhala mp3 jayasrilanka
And great to find it at the top of Google search. Anon Feb 19 :. However, what I am looking for is slightly unusual use case. I am looking for something that will allow me to define the onload and onerror functions at the prototype level, for example:. Ibrahima Diallo Feb 19 :. That's a great question and unfortunately the answer is, you can't. Native functions prototypes cannot be overwritten.
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