svelte-lazy-image/README.md

Svelte component to lazy load images using Intersection Observer

# svelte-lazy-image

Svelte component to lazy load images using [Intersection Observer](https://developer.mozilla.org/en-US/docs/Web/API/Intersection_Observer_API).

## Usage

```bash
npm install svelte-lazy-image
```

### Svelte:

#### use:action

Set `data-src` and/or `data-srcset` on an `img` element:

```html
<script>
	import { useLazyImage as lazyImage } from 'svelte-lazy-image';
</script>

<img data-src="https://via.placeholder.com/250?text=src1" alt="foobar" use:lazyImage />
```

Specify IntersectionObserver [options](https://developer.mozilla.org/en-US/docs/Web/API/IntersectionObserver/IntersectionObserver) via object passed to `use`:

```html
<script>
	import { LazyImage, useLazyImage as lazyImage } from 'svelte-lazy-image';
</script>

<img src="https://via.placeholder.com/250?text=placeholder1"
data-src="https://via.placeholder.com/250?text=src1" alt="foobar" use:lazyImage={{ threshold: 0.5 }}
/>
```

#### Component

```html
<script>
	import { LazyImage } from 'svelte-lazy-image';
</script>

<LazyImage
	src="https://via.placeholder.com/250?text=src"
	placeholder="https://via.placeholder.com/250?text=placeholder"
	alt="Lorem Ipsum"
/>
```

The component uses `$$restProps` to pass props other than `placeholder`, `src`, or `alt` to the underlying `img` element. An example using `img` attributes `srcset` and `sizes`:

```html
<script>
	import { LazyImage } from 'svelte-lazy-image';
</script>

<LazyImage
	src="https://via.placeholder.com/250?text=src"
	placeholder="https://via.placeholder.com/250?text=placeholder"
	alt="Lorem Ipsum"
	srcset="https://via.placeholder.com/480 480w, https://via.placeholder.com/800 800w"
	sizes="(max-width: 600px) 480px, 800px"
/>
```

Specify IntersectionObserver [options](https://developer.mozilla.org/en-US/docs/Web/API/IntersectionObserver/IntersectionObserver):

```html
<script>
  import { LazyImage } from 'svelte-lazy-image';
</script>

<LazyImage
  src="https://via.placeholder.com/250?text=src"
  placeholder="https://via.placeholder.com/250?text=placeholder"
  alt="Lorem Ipsum"
  options={{ threshold: 0.5 }}
/>
```