apoorvsaxena/lozad.js

🔥 Highly performant, light ~1kb and configurable lazy loader in pure JS with no dependencies for responsive images, iframes and more

lozad.js's Issues

Feature request: Low Quality Image Placeholders (LQIP)

Would it be possible to keep the current behavior but once the image appears on the screen first load a lower quality image and then the final image?
This would reduce the time in which the image isn't display once the user reaches it.

Add git hooks

Add git hooks to prevent bad commits, by runing the linter and/or the tests before any commit. Could be used husky.

Not working in Edge

Demo not working in latest Edge. No errors in console.

Why selectorClass?

It seems like selectorClass is too specific.

It would be better to use selector so one could do the following:

new Lozad({
  selector: 'img',
  threshold: 0.1
})

Or the following:

new Lozad({
  selector: '#jumbo',
  threshold: 0.1
})

Of course you could still select by class, just add a dot.

new Lozad({
  selector: '.lozad',
  threshold: 0.1
})

Support passing an `Element` or `NodeList`

It would be really useful to be able to pass either an Element or NodeList as well as a string selector.

For example:

const node = document.querySelector('img')
lozad(node)

or

const nodes = document.querySelectorAll('img')
lozad(nodes)

I'm using Lozad in a web component context, where I don't want to select my DOM node from the document, but rather some local tree. Being able to pass in the reference to the node(s) myself makes this trivial.

I have made the changes in a forked branch as a proof of concept, which I am happy to PR if there is agreement around the idea!

Forked branch: https://github.com/chrishutchinson/lozad.js/tree/feature/passElementOrNodeList

Preloader

Would like to make a preloader
Believe that users should have a indication of a loading element.
Is there an .is-loading class or something.

How can achieve this, thanks?

deprecating Bower support

Considering that:

• Bower itself has been recommending use of Yarn for package installation
• No way to automate publishing update to bower
• most of the users are using jsDeliver CDN with ~1M downloads/month or npm package

thanks to @thiamsantos for suggesting this before as well, with data it's evident now that folks are using CDN directly or Yarn installation only.

If image are after lozad init, image are not loaded

Hi,

This library is really impressive, but I just realized that if an image is placed after initialization, it is never loaded.

I have made a little jsbin : https://jsbin.com/bofurugene/2/edit?html,output
And the 100*200 pic never load

So, how to do ?

Thanks.

srcset

Is it possible to add support for "srcset"?

How to use placeholder images

One fast question. Do I myself need to implement the logic for placeholder images?

Srcset

Does your plugin work with srcset? Or only with src?

Kebab-case classes are not fired

Following the documentation, to pick a typical CSS kebab-case class, does not make the plugin fire.

E.g.:

const observer = lozad('.is-lazy')

After update to 1.0.7, data-background-image is no longer working

I can see it was changed in 068b395 from element.dataset.backgroundImage to element.getAttribute('data-backgroundImage')

But guess it should be element.getAttribute('data-background-image') instead?

Add a editorconfig

Add editorconfig to keep a consistent coding style in the project.

See my personal editorconfig as example.

Use ES6

Would be great to use ES6 in the project and let Babel and rollup handle all the transpilation complexity.

Amend readme to show use of <noscript> fallback

As per previous issue.

Is this project willing take pull request of typescript definitions?

It will be useful for typescript users and improve the experiences on some editors like vscode.

basicly a index.d.ts file with:

type Option = {
    rootMargin?: string;
    threshold?: number;
    load?(element: HTMLElement | HTMLCanvasElement): void;
}

type Observer = {
    observe(): void;
}

declare function lozad(selector?: string, options?: Option): Observer;

declare namespace lozad {
    const prototype: {
    };
}

export as namespace lozad;

export = lozad;

Remove dist folder from git

Remove dist folder from to git as it is a file automatically generated and we don't need to keep track of them. In that way would be possible to keep the pull requests more clean. To accomplish this just add the dist folder to the gitignore file and add a files property to the package.json specifying the files to be included in the package when download it from npm. Right now all the repo is included.

The only problem that I can see on doing this is that the demo uses a relative path to the dist folder. But the demo can pull the project from a cdn (related #17).

Improve contributing guidelines

Do something inspired on awesome projects out there like atom. I personally use a simplified version of these guidelines in my projects.

Improvement

Hi @ApoorvSaxena ,

I've just discovered an other library using intersection observer to lazyload image with some interesting approach.

You should have a look to the code some part of it could be interesting to improve lozad.js 😄

https://github.com/marlospomin/turtle/blob/master/src/turtle.js

Cheers

No Fallback for when Javascript fails to load ?

Is a fallback part of the task list? for when Javascript fails to load.

Not working in Safari on Mac

In last Safari (10.1.2) images dont load. Error in console: "Can't find variable: IntersectionObserver".

iframes

Where is demo and documentation about lazyloading iframes?

Automate publish to npm and bower using travis

Travis has an API to publish to npm. A bower publish could be triggered when travis finishes to publish to npm using the bower cli api. After that done may be easy to remove the dist from the repository (ref #18).

List of websites using Lozad.js

Will be adding list of such websites in README.

Use travis

Add a simple build step on travis to show the people that the package has no errors.

IE9 not working - loader Issue

When emulating IE9, images do not load because of the following error:

The "loaded" property of an undefined or null reference can not be retrieved.

Seems like it hase something to do with the loaded statement. I tried to fix it but I failed:

t.dataset.loaded=!0

Any help would be appreciated.

Thanks,

Sebastian

P.S. Adding the Polyfill does not work either. As far as I understand, Polyfill only helps for IE Versions Prior 9.

Testing for image element

Hi! Thanks for the awesome library!

I was wondering if it would be an idea to actually test for the img element in the check that you do? Seeing that the src attribute can only be applied to a limited amount of elements, it would be easy to test for those and add specific functionality for them, and otherwise for background images. This way we can give the background image a regular data-src as well, instead of the data-background-image we've got now.

Something like:

if (element.tagName === 'IMG') {
  if (element.dataset.src) {
    element.src = element.dataset.src;
  }
  if (element.dataset.srcset) {
    element.srcset = element.dataset.srcset;
  }
} else {
  element.style.backgroundImage = `url(${element.dataset.src})`;
}

maybe?

React Support?

I was wondering if Lozad works with react? I'm currently having trouble getting it work, I was trying to utilize lifecycle methods and have it not start observing until after the component is rendered. However, it seems like based on the nature of react and vdom, it doesn't actually work because my component is rendered before Lozad is initialized.

Any ideas? I was trying something along the lines of:

    observer = lozad('.lozad', {
        load: function() { console.log('loaded'); }
    });

    componentDidMount() {
        this.observer.observe();
    }

Thanks in advanced!

Support videos and components

Hi all,
i worked on a similar library few weeks ago. Besides <img> elements, i got <video> and components which need own (heavy) JS to lazy load as well: https://github.com/midzer/lazyobs

Maybe we can merge some ideas into this project :)

Cheers
midzer

Threshold not working

Hi,

I was reading the official documentation to understand how Intersection observer work:

https://developer.mozilla.org/en-US/docs/Web/API/Intersection_Observer_API#Intersection_observer_options

But while making some tests to fine tune, I've notice that changing threshold to any value doesn't delay the callback at all.

For exemple, the callback should wait until all pixel are in view if the threshold is set to 1 but that's not the case.

Am I the only one with this problem?

Cheers

With JavaScript off, no images are shown.

https://apoorv.pro/lozad.js/demo/

(because no src="" attribute on img elements for fallback. Also, alt attribute is malformed; should be alt="")

add dev server

I think add a script just like npm run dev. It can see the example and it's convenient to debug and coding lozad.js

Check if image is loaded?

It seems that in a gallery with a large numbers of items it can happen that data-loaded=true or any class you add in the callback, for that matters, can be applied to an image while the background image is not yet fully loaded. This results in a suddenly appearing image (especially when the images itself are fairly large) because the transition was already applied before the image was loaded in the browser.

I would propose to test if the image is actually loaded before adding the data-loaded=true attribute. Maybe like

const imgLoad = new Image();
imgLoad.onload = () => {
  element.dataset.loaded = true;
}
imgLoad.src = element.dataset.src;

There might be better ways to check if the images are loaded, but you catch my drift :)

edit: This does lead to the loading of two files when the srcset file which is loaded is different from the src file. This could be fixed by polling if element.currentSrc is set and use that image for the imgLoad.src.

lozad.js with picture-element to use src from source

Hi there,

First of all great work, much appreciated!

I'm using lozad with the <picture> element like the following structure:

<picture>
    <!--[if IE 9]><video style="display: none;"><![endif]-->
      <source media="(min-width: 1024px)" data-srcset="...">
      <source media="(min-width: 768px)" data-srcset="...">
      <source data-srcset="...">
    <!--[if IE 9]></video><![endif]-->
    <img class="lozad" data-src="" alt="...">
</picture>

It happens that the final rendered image gets the data-src of the <img>-tag as its src rather than the desired source coming from the srcset of the matching <source>. Did I miss anything in the code above? I initialize it via simply calling observer.observe();

Thanks a lot for getting back to me,
Stefan

add basic test cases

deleted

deleted

update documentation

• mention about sites using Lozad.js

provide a polyfill

IntersectionObserver is high version api https://caniuse.com/#search=IntersectionObserver. I think we can provide a polyfill version. what do you think?

Expose a function to load specific images before they appear

It would be useful to be able to preload certain images in advance when certain events are triggered (say, a menu is opened). Currently, though, the load function is not exported from the module. It would be useful to reuse it instead of having to write it by yourself.

The only issue I see is that the load function is configurable. Although I suppose, we could assign it to the lozad object.

Example:

import lozad from 'lozad'

const observer = lozad()
observer.observe()
document.addEventListener('menu:open', () => {
  observer.load('img.language-icon')
})

Though observer.load doesn't sound right.

Change method signature

What do you think about changing the method signature from this:

const lozad = new Lozad({
    selectorClass: 'lozad', // for identification of images to lazy load
    rootMargin: '10px 0px', // syntax similar to that of CSS Margin
    threshold: 0.1 // ratio of image convergence
})
lozad.load = function(el) {
	console.log('loading element');
}

For something like this:

lozad('.some-selector', {
  rootMargin: '10px 0px',
  threshold: 0.1,
  onLoad() {
    console.log('loading element')
  }
})

In that way we would follow some good patterns followed by big libraries out there like moment. Additionally eslint has a rule that discourages the use of new for side effects. There a whole talk about that, I think that would be good if you check it out.

Best regards.

Polyfill IntersectionObserver

IntersectionObserver is not supported entirely for all the browsers, see here

Make sure we polyfill it optionally, so anyone that wants to support those browsers, can apply this library.

Let's use the official one: https://github.com/w3c/IntersectionObserver/tree/master/polyfill

holp it supports specifying observe container

lozad.js/src/lozad.js

Lines 47 to 49 in 65f9744

	return {
	observe() {
	const elements = document.querySelectorAll(selector)

if the document can be replaced by a specified dom, it will be greater!
Maybe like this:

observe( { container = document } ) { 
     const elements = container.querySelectorAll(selector) 
}

Put the demo on a separated branch

Does lozad.js support lazy load of background images? I am working on a project that has multiple background images in each section and I current preload the images, but I would like to use your script if this can be done.

Make placeholder div

can we make a div placeholder that will be shown before image fully loads, so images will not jump around

Demo not working

There is a 404 error with the polyfill file:
https://rawgithub.com/w3c/IntersectionObserver/gh-pages/polyfill/intersection-observer.js

It seems that the file has been removed on branch "gh-pages" over at:
https://github.com/w3c/IntersectionObserver/tree/gh-pages/polyfill

display size of lozad.js via badge

Update Readme

Update readme to respect the standard-readme spec.

add test case for triggerLoad function