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native-lazy-loading

1.0.1 • Public • Published

native-lazy-loading

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Add the loading attribute to completely defer the loading of offscreen images and iframes that can be reached by scrolling:

<img src="image.png" loading="lazy" alt="" width="200" height="200">
<iframe src="https://example.com" loading="lazy"></iframe>

Here are the supported values for the loading attribute:

  • auto: Default lazy-loading behavior of the browser, which is the same as not including the attribute.
  • lazy: Defer loading of the resource until it reaches a calculated distance from the viewport.
  • eager: Load the resource immediately, regardless of where it's located on the page.

This feature introduced starting with Chrome 76. The loading attribute should not affect code that currently lazy-loads your assets in any way. It is important to continue to use a third-party library along with loading="lazy" is to provide a polyfill for browsers that do not yet support the attribute.

If you are not using any third-party library so this plugin helps you to do that. This plugin replaces src with data-src to avoid an eager load in unsupported browsers. By default, it adds the lazyload class if you enable compatibility. You need to add the below-mentioned script before closing the </body> tag to use lazysizes in unsupported browsers. Lazysizes is a popular JavaScript lazy-loading library recommended by web.dev.

loading attribute with lazysizes

<script>
  if ('loading' in HTMLImageElement.prototype) {
    const images = document.querySelectorAll('.native-lazy-loading');
    images.forEach(img => {
      if (img.dataset.src) {
        img.src = img.dataset.src;
      }
    });
  } else {
    // Dynamically import the LazySizes library
    const script = document.createElement('script');
    script.src = 'https://cdnjs.cloudflare.com/ajax/libs/lazysizes/4.1.8/lazysizes.min.js';
    document.body.appendChild(script);
  }
</script>

If you don't like to use the loading attribute and want to disable it so just pass the  defaultValue: ''  as shown in Disable Native Load and use lazysizes library example. In this case, you need to add the below-mentioned script before closing the </body> tag.

Use lazysizes without loading attribute

<script>
  // Dynamically import the LazySizes library
  const script = document.createElement('script');
  script.src = 'https://cdnjs.cloudflare.com/ajax/libs/lazysizes/4.1.8/lazysizes.min.js';
  document.body.appendChild(script);
</script>

Install

Via npm

npm install native-lazy-loading

Via Yarn

yarn add native-lazy-loading

Usage

Import Package in Node.js.

var nativeLazyLoading = require('native-lazy-loading');

Import Package in React.

import nativeLazyLoading from 'native-lazy-loading';

Parameters

Attributes Type Required Default Description
html String Yes HTML in which loading attribute needs to be applied on image and iframe tags.
options Object No loading="lazy" By default, it adds loading="lazy" in images and iframe tags. If you like to apply different loading attributes OR only apply loading attributes in a specific image and iframe then you use this attribute.

You can find more details in Examples with loading attribute only.
compatibility Boolean No false Just pass true if you like to apply lazysizes or any other third-party lazyload for the unsupported browsers/versions with the help of this package.

By enabling this, It will do the following things:

1. Change src to data-src
2. Add custom class like lazyload by default which is used by lazysizes.
3. Add placeholder image if set in library attribute.

Check Examples with loading attribute and unsupported browsers for further details
library Object No class: 'lazyload' This option is used if you like to use any third party lazyload other than lazysizes to handle browsers that don't yet support native lazy-loading.

options Attributes

Attributes Type Required Default Description
auto Array No Class array on which you like to apply auto value of loading attribute.
lazy Array No Class array on which you like to apply lazy value of loading attribute.
eager Array No Class array on which you like to apply eager value of loading attribute.
defaultValue String No lazy This is applicable on all the other image and iframe tags which don't have any class OR which have class but not matched with any of the defined classes.

For further details, please check the example 2 and example 3 under Examples with loading attribute only.

library Attributes

Attributes Type Required Default Description
class String No lazyload Every lazyload library works on its defined class. You can set the class name from here.
newSrc String No To load placeholder image like loading.gif, you can use this attribute.
notAllowed Array No To avoid using any third-party lazyload library in any specific image and/or iframe tag you can add its class name in this attribute.

No compatibility changes will be made on the matched classes. For further clarification check this example.

Examples with loading attribute only

Add loading="lazy" attribute on all images and iFrames

const nativeLazyLoading = require('native-lazy-loading');
var html = `<img src="https://www.yasglobal.com/wp-content/themes/yasglobal/images-cus/logo.svg" alt="YAS Global Logo" title="YAS Global Logo" class="no-lazy"/>
            <div class="white logos">
              <div class="container">
                <div class="testimonials">
                  <div class="item">
                    <img src="/wordpress-logo.svg" style="margin-top: -9px;" alt="WordPress Logo" title="WordPress Logo" class="testing-lazyload" />
                  </div>
                  <div class="item">
                    <img src="/drupal-logo.svg" style="margin-top: -9px;" alt="Drupal Logo" title="Drupal Logo" class="testing-lazyload" />
                  </div>
                  <div class="item">
                    <img src="/contentful-logo.svg" style="margin-top: -9px;" alt="Contentful Logo" title="Contentful Logo" class="testing-lazyload" />
                  </div>
                  <div class="item">
                    <img src="/contentstack-logo.svg" style="margin-top: -9px;" alt="ContentStack Logo" title="ContentStack Logo" class="testing-lazyload" />
                  </div>
                  <div class="item">
                    <img src="/netlify-logo.svg" style="margin-top: -9px;" alt="Netlify Logo" title="Netlify Logo" class="testing-lazyload" />
                  </div>
                  <div class="item">
                    <img src="/heroku-logo.svg" style="margin-top: -9px;" alt="Heroku Logo" title="Heroku Logo" class="testing-lazyload" />
                  </div>
                  <div class="item">
                    <img src="/pantheon-logo.svg" style="margin-top: -9px;" alt="Pantheon Logo" title="Pantheon Logo" class="testing-lazyload" />
                  </div>
                  <div class="item">
                    <img src="/wpengine-logo.svg" style="margin-top: -9px;" alt="WP Engine Logo" title="WP Engine Logo" class="testing-lazyload" />
                  </div>
                </div>
 
                <iframe src="https://www.w3schools.com" name="w3schools" class="testing-lazyload"></iframe>
              </div>
            </div>`;
 
html = nativeLazyLoading(html);
 
console.log(html);

Add loading="lazy" attribute on all images and iFrames except on no-lazy and header-images class

const nativeLazyLoading = require('native-lazy-loading');
var html = `<img src="https://www.yasglobal.com/wp-content/themes/yasglobal/images-cus/logo.svg" alt="YAS Global Logo" title="YAS Global Logo" class="no-lazy"/>
            <div class="white logos">
              <div class="container">
                <div class="testimonials">
                  <div class="item">
                    <img src="/wordpress-logo.svg" style="margin-top: -9px;" alt="WordPress Logo" title="WordPress Logo" class="testing-lazyload" />
                  </div>
                  <div class="item">
                    <img src="/drupal-logo.svg" style="margin-top: -9px;" alt="Drupal Logo" title="Drupal Logo" class="testing-lazyload" />
                  </div>
                  <div class="item">
                    <img src="/contentful-logo.svg" style="margin-top: -9px;" alt="Contentful Logo" title="Contentful Logo" class="testing-lazyload" />
                  </div>
                  <div class="item">
                    <img src="/contentstack-logo.svg" style="margin-top: -9px;" alt="ContentStack Logo" title="ContentStack Logo" class="testing-lazyload" />
                  </div>
                  <div class="item">
                    <img src="/netlify-logo.svg" style="margin-top: -9px;" alt="Netlify Logo" title="Netlify Logo" class="testing-lazyload" />
                  </div>
                  <div class="item">
                    <img src="/heroku-logo.svg" style="margin-top: -9px;" alt="Heroku Logo" title="Heroku Logo" class="testing-lazyload" />
                  </div>
                  <div class="item">
                    <img src="/pantheon-logo.svg" style="margin-top: -9px;" alt="Pantheon Logo" title="Pantheon Logo" class="testing-lazyload" />
                  </div>
                  <div class="item">
                    <img src="/wpengine-logo.svg" style="margin-top: -9px;" alt="WP Engine Logo" title="WP Engine Logo" class="testing-lazyload" />
                  </div>
                </div>
 
                <iframe src="https://www.w3schools.com" name="w3schools" class="testing-lazyload"></iframe>
              </div>
            </div>`;
 
html = nativeLazyLoading(html, {
  auto: ['no-lazy', 'header-images']
});
 
console.log(html);

NOTE: auto means the same as not including the attribute.

Add loading="lazy" attribute on only images and iFrames which contains testing-lazyload class

const nativeLazyLoading = require('native-lazy-loading');
var html = `<img src="https://www.yasglobal.com/wp-content/themes/yasglobal/images-cus/logo.svg" alt="YAS Global Logo" title="YAS Global Logo" class="no-lazy"/>
            <div class="white logos">
              <div class="container">
                <div class="testimonials">
                  <div class="item">
                    <img src="/wordpress-logo.svg" style="margin-top: -9px;" alt="WordPress Logo" title="WordPress Logo" class="testing-lazyload" />
                  </div>
                  <div class="item">
                    <img src="/drupal-logo.svg" style="margin-top: -9px;" alt="Drupal Logo" title="Drupal Logo" class="testing-lazyload" />
                  </div>
                  <div class="item">
                    <img src="/contentful-logo.svg" style="margin-top: -9px;" alt="Contentful Logo" title="Contentful Logo" class="testing-lazyload" />
                  </div>
                  <div class="item">
                    <img src="/contentstack-logo.svg" style="margin-top: -9px;" alt="ContentStack Logo" title="ContentStack Logo" class="testing-lazyload" />
                  </div>
                  <div class="item">
                    <img src="/netlify-logo.svg" style="margin-top: -9px;" alt="Netlify Logo" title="Netlify Logo" class="testing-lazyload" />
                  </div>
                  <div class="item">
                    <img src="/heroku-logo.svg" style="margin-top: -9px;" alt="Heroku Logo" title="Heroku Logo" class="testing-lazyload" />
                  </div>
                  <div class="item">
                    <img src="/pantheon-logo.svg" style="margin-top: -9px;" alt="Pantheon Logo" title="Pantheon Logo" class="testing-lazyload" />
                  </div>
                  <div class="item">
                    <img src="/wpengine-logo.svg" style="margin-top: -9px;" alt="WP Engine Logo" title="WP Engine Logo" class="testing-lazyload" />
                  </div>
                </div>
 
                <iframe src="https://www.w3schools.com" name="w3schools" class="testing-lazyload"></iframe>
              </div>
            </div>`;
 
html = nativeLazyLoading(html, {
  lazy: ['testing-lazyload'],
  defaultValue: ''
});
 
console.log(html);

Examples with loading attribute and unsupported browsers

Add loading="lazy" attribute on all images and iFrames with lazysizes class

const nativeLazyLoading = require('native-lazy-loading');
var html = `<img src="https://www.yasglobal.com/wp-content/themes/yasglobal/images-cus/logo.svg" alt="YAS Global Logo" title="YAS Global Logo" class="no-lazy"/>
            <div class="white logos">
              <div class="container">
                <div class="testimonials">
                  <div class="item">
                    <img src="/wordpress-logo.svg" style="margin-top: -9px;" alt="WordPress Logo" title="WordPress Logo" class="testing-lazyload" />
                  </div>
                  <div class="item">
                    <img src="/drupal-logo.svg" style="margin-top: -9px;" alt="Drupal Logo" title="Drupal Logo" class="testing-lazyload" />
                  </div>
                  <div class="item">
                    <img src="/contentful-logo.svg" style="margin-top: -9px;" alt="Contentful Logo" title="Contentful Logo" class="testing-lazyload" />
                  </div>
                  <div class="item">
                    <img src="/contentstack-logo.svg" style="margin-top: -9px;" alt="ContentStack Logo" title="ContentStack Logo" class="testing-lazyload" />
                  </div>
                  <div class="item">
                    <img src="/netlify-logo.svg" style="margin-top: -9px;" alt="Netlify Logo" title="Netlify Logo" class="testing-lazyload" />
                  </div>
                  <div class="item">
                    <img src="/heroku-logo.svg" style="margin-top: -9px;" alt="Heroku Logo" title="Heroku Logo" class="testing-lazyload" />
                  </div>
                  <div class="item">
                    <img src="/pantheon-logo.svg" style="margin-top: -9px;" alt="Pantheon Logo" title="Pantheon Logo" class="testing-lazyload" />
                  </div>
                  <div class="item">
                    <img src="/wpengine-logo.svg" style="margin-top: -9px;" alt="WP Engine Logo" title="WP Engine Logo" class="testing-lazyload" />
                  </div>
                </div>
 
                <iframe src="https://www.w3schools.com" name="w3schools" class="testing-lazyload"></iframe>
              </div>
            </div>`;
 
html = nativeLazyLoading(html, {}, true);
 
console.log(html);

Add loading="lazy" attribute on all images and iFrames with custom class

const nativeLazyLoading = require('native-lazy-loading');
var html = `<img src="https://www.yasglobal.com/wp-content/themes/yasglobal/images-cus/logo.svg" alt="YAS Global Logo" title="YAS Global Logo" class="no-lazy"/>
            <div class="white logos">
              <div class="container">
                <div class="testimonials">
                  <div class="item">
                    <img src="/wordpress-logo.svg" style="margin-top: -9px;" alt="WordPress Logo" title="WordPress Logo" class="testing-lazyload" />
                  </div>
                  <div class="item">
                    <img src="/drupal-logo.svg" style="margin-top: -9px;" alt="Drupal Logo" title="Drupal Logo" class="testing-lazyload" />
                  </div>
                  <div class="item">
                    <img src="/contentful-logo.svg" style="margin-top: -9px;" alt="Contentful Logo" title="Contentful Logo" class="testing-lazyload" />
                  </div>
                  <div class="item">
                    <img src="/contentstack-logo.svg" style="margin-top: -9px;" alt="ContentStack Logo" title="ContentStack Logo" class="testing-lazyload" />
                  </div>
                  <div class="item">
                    <img src="/netlify-logo.svg" style="margin-top: -9px;" alt="Netlify Logo" title="Netlify Logo" class="testing-lazyload" />
                  </div>
                  <div class="item">
                    <img src="/heroku-logo.svg" style="margin-top: -9px;" alt="Heroku Logo" title="Heroku Logo" class="testing-lazyload" />
                  </div>
                  <div class="item">
                    <img src="/pantheon-logo.svg" style="margin-top: -9px;" alt="Pantheon Logo" title="Pantheon Logo" class="testing-lazyload" />
                  </div>
                  <div class="item">
                    <img src="/wpengine-logo.svg" style="margin-top: -9px;" alt="WP Engine Logo" title="WP Engine Logo" class="testing-lazyload" />
                  </div>
                </div>
 
                <iframe src="https://www.w3schools.com" name="w3schools" class="testing-lazyload"></iframe>
              </div>
            </div>`;
 
html = nativeLazyLoading(html, {}, true, {
  class: 'lazy'
});
 
console.log(html);

Add loading="lazy" attribute on all images and iFrames with custom class except on no-lazy class

const nativeLazyLoading = require('native-lazy-loading');
var html = `<img src="https://www.yasglobal.com/wp-content/themes/yasglobal/images-cus/logo.svg" alt="YAS Global Logo" title="YAS Global Logo" class="no-lazy"/>
            <div class="white logos">
              <div class="container">
                <div class="testimonials">
                  <div class="item">
                    <img src="/wordpress-logo.svg" style="margin-top: -9px;" alt="WordPress Logo" title="WordPress Logo" class="testing-lazyload" />
                  </div>
                  <div class="item">
                    <img src="/drupal-logo.svg" style="margin-top: -9px;" alt="Drupal Logo" title="Drupal Logo" class="testing-lazyload" />
                  </div>
                  <div class="item">
                    <img src="/contentful-logo.svg" style="margin-top: -9px;" alt="Contentful Logo" title="Contentful Logo" class="testing-lazyload" />
                  </div>
                  <div class="item">
                    <img src="/contentstack-logo.svg" style="margin-top: -9px;" alt="ContentStack Logo" title="ContentStack Logo" class="testing-lazyload" />
                  </div>
                  <div class="item">
                    <img src="/netlify-logo.svg" style="margin-top: -9px;" alt="Netlify Logo" title="Netlify Logo" class="testing-lazyload" />
                  </div>
                  <div class="item">
                    <img src="/heroku-logo.svg" style="margin-top: -9px;" alt="Heroku Logo" title="Heroku Logo" class="testing-lazyload" />
                  </div>
                  <div class="item">
                    <img src="/pantheon-logo.svg" style="margin-top: -9px;" alt="Pantheon Logo" title="Pantheon Logo" class="testing-lazyload" />
                  </div>
                  <div class="item">
                    <img src="/wpengine-logo.svg" style="margin-top: -9px;" alt="WP Engine Logo" title="WP Engine Logo" class="testing-lazyload" />
                  </div>
                </div>
 
                <iframe src="https://www.w3schools.com" name="w3schools" class="testing-lazyload"></iframe>
              </div>
            </div>`;
 
html = nativeLazyLoading(html, {}, true, {
  class: 'lazy',
  notAllowed: ['no-lazy']
});
 
console.log(html);

NOTE: Make sure to add the script as mentioned in the description before closing the </body> tag if you are willing to use lazysizes for unsupported versions/browsers.

Examples without loading attribute

Disable Native Load and use lazysizes library

const nativeLazyLoading = require('native-lazy-loading');
var html = `<img src="https://www.yasglobal.com/wp-content/themes/yasglobal/images-cus/logo.svg" alt="YAS Global Logo" title="YAS Global Logo" class="no-lazy"/>
            <div class="white logos">
              <div class="container">
                <div class="testimonials">
                  <div class="item">
                    <img src="/wordpress-logo.svg" style="margin-top: -9px;" alt="WordPress Logo" title="WordPress Logo" class="testing-lazyload" />
                  </div>
                  <div class="item">
                    <img src="/drupal-logo.svg" style="margin-top: -9px;" alt="Drupal Logo" title="Drupal Logo" class="testing-lazyload" />
                  </div>
                  <div class="item">
                    <img src="/contentful-logo.svg" style="margin-top: -9px;" alt="Contentful Logo" title="Contentful Logo" class="testing-lazyload" />
                  </div>
                  <div class="item">
                    <img src="/contentstack-logo.svg" style="margin-top: -9px;" alt="ContentStack Logo" title="ContentStack Logo" class="testing-lazyload" />
                  </div>
                  <div class="item">
                    <img src="/netlify-logo.svg" style="margin-top: -9px;" alt="Netlify Logo" title="Netlify Logo" class="testing-lazyload" />
                  </div>
                  <div class="item">
                    <img src="/heroku-logo.svg" style="margin-top: -9px;" alt="Heroku Logo" title="Heroku Logo" class="testing-lazyload" />
                  </div>
                  <div class="item">
                    <img src="/pantheon-logo.svg" style="margin-top: -9px;" alt="Pantheon Logo" title="Pantheon Logo" class="testing-lazyload" />
                  </div>
                  <div class="item">
                    <img src="/wpengine-logo.svg" style="margin-top: -9px;" alt="WP Engine Logo" title="WP Engine Logo" class="testing-lazyload" />
                  </div>
                </div>
 
                <iframe src="https://www.w3schools.com" name="w3schools" class="testing-lazyload"></iframe>
              </div>
            </div>`;
 
html = nativeLazyLoading(
  html, {
    defaultValue: ''
  },
  true
);
 
console.log(html);

NOTE: Make sure to add the script as mentioned in the description before closing the </body> tag.

Return

HTML with adding loading attribute on image and iFrame tags. Also, change src with data-src if compatibility set to true and apply the lazysizes class for unsupported browsers, if you like to apply a separate class then you can define it in library object.

Tested

This package is tested with the Node.js and React Application.

Install

npm i native-lazy-loading

DownloadsWeekly Downloads

467

Version

1.0.1

License

MIT

Unpacked Size

40.8 kB

Total Files

5

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