355 lines
8.9 KiB
TypeScript
355 lines
8.9 KiB
TypeScript
import React, { ReactElement, useEffect, useRef } from 'react'
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import Head from '../next-server/lib/head'
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const VALID_LOADING_VALUES = ['lazy', 'eager', undefined] as const
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type LoadingValue = typeof VALID_LOADING_VALUES[number]
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const loaders = new Map<LoaderKey, (props: LoaderProps) => string>([
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['imgix', imgixLoader],
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['cloudinary', cloudinaryLoader],
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['akamai', akamaiLoader],
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['default', defaultLoader],
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])
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type LoaderKey = 'imgix' | 'cloudinary' | 'akamai' | 'default'
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type ImageData = {
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sizes: number[]
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loader: LoaderKey
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path: string
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}
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type ImageProps = Omit<
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JSX.IntrinsicElements['img'],
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'src' | 'srcSet' | 'ref' | 'width' | 'height' | 'loading'
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> & {
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src: string
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quality?: string
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priority?: boolean
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loading?: LoadingValue
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unoptimized?: boolean
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} & (
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| { width: number | string; height: number | string; unsized?: false }
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| { width?: number | string; height?: number | string; unsized: true }
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)
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const imageData: ImageData = process.env.__NEXT_IMAGE_OPTS as any
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const { sizes: configSizes, loader: configLoader, path: configPath } = imageData
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configSizes.sort((a, b) => a - b) // smallest to largest
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const largestSize = configSizes[configSizes.length - 1]
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let cachedObserver: IntersectionObserver
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const IntersectionObserver =
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typeof window !== 'undefined' ? window.IntersectionObserver : null
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function getObserver(): IntersectionObserver | undefined {
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// Return shared instance of IntersectionObserver if already created
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if (cachedObserver) {
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return cachedObserver
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}
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// Only create shared IntersectionObserver if supported in browser
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if (!IntersectionObserver) {
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return undefined
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}
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return (cachedObserver = new IntersectionObserver(
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(entries) => {
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entries.forEach((entry) => {
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if (entry.isIntersecting) {
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let lazyImage = entry.target as HTMLImageElement
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if (lazyImage.dataset.src) {
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lazyImage.src = lazyImage.dataset.src
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}
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if (lazyImage.dataset.srcset) {
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lazyImage.srcset = lazyImage.dataset.srcset
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}
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lazyImage.style.visibility = 'visible'
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lazyImage.classList.remove('__lazy')
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cachedObserver.unobserve(lazyImage)
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}
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})
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},
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{ rootMargin: '200px' }
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))
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}
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function computeSrc(
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src: string,
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unoptimized: boolean,
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quality?: string
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): string {
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if (unoptimized) {
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return src
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}
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return callLoader({ src, width: largestSize, quality })
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}
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type CallLoaderProps = {
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src: string
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width: number
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quality?: string
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}
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function callLoader(loaderProps: CallLoaderProps) {
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const load = loaders.get(configLoader) || defaultLoader
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return load({ root: configPath, ...loaderProps })
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}
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type SrcSetData = {
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src: string
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widths: number[]
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quality?: string
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}
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function generateSrcSet({ src, widths, quality }: SrcSetData): string {
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// At each breakpoint, generate an image url using the loader, such as:
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// ' www.example.com/foo.jpg?w=480 480w, '
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return widths
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.map((width: number) => `${callLoader({ src, width, quality })} ${width}w`)
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.join(', ')
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}
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type PreloadData = {
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src: string
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widths: number[]
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sizes?: string
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unoptimized?: boolean
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quality?: string
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}
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function generatePreload({
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src,
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widths,
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unoptimized = false,
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sizes,
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quality,
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}: PreloadData): ReactElement {
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// This function generates an image preload that makes use of the "imagesrcset" and "imagesizes"
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// attributes for preloading responsive images. They're still experimental, but fully backward
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// compatible, as the link tag includes all necessary attributes, even if the final two are ignored.
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// See: https://web.dev/preload-responsive-images/
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return (
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<Head>
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<link
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rel="preload"
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as="image"
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href={computeSrc(src, unoptimized, quality)}
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// @ts-ignore: imagesrcset and imagesizes not yet in the link element type
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imagesrcset={generateSrcSet({ src, widths, quality })}
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imagesizes={sizes}
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/>
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</Head>
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)
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}
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export default function Image({
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src,
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sizes,
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unoptimized = false,
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priority = false,
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loading,
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className,
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quality,
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width,
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height,
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unsized,
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...rest
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}: ImageProps) {
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const thisEl = useRef<HTMLImageElement>(null)
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if (process.env.NODE_ENV !== 'production') {
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if (!VALID_LOADING_VALUES.includes(loading)) {
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throw new Error(
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`Image with src "${src}" has invalid "loading" property. Provided "${loading}" should be one of ${VALID_LOADING_VALUES.map(
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String
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).join(',')}.`
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)
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}
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if (priority && loading === 'lazy') {
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throw new Error(
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`Image with src "${src}" has both "priority" and "loading=lazy" properties. Only one should be used.`
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)
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}
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}
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let lazy = loading === 'lazy'
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if (!priority && typeof loading === 'undefined') {
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lazy = true
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}
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useEffect(() => {
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const target = thisEl.current
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if (target && lazy) {
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const observer = getObserver()
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if (observer) {
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observer.observe(target)
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return () => {
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observer.unobserve(target)
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}
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}
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}
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}, [thisEl, lazy])
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// Generate attribute values
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const imgSrc = computeSrc(src, unoptimized, quality)
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const imgSrcSet = !unoptimized
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? generateSrcSet({
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src,
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widths: configSizes,
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quality,
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})
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: undefined
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let imgAttributes:
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| {
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src: string
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srcSet?: string
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}
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| {
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'data-src': string
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'data-srcset'?: string
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}
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if (!lazy) {
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imgAttributes = {
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src: imgSrc,
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}
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if (imgSrcSet) {
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imgAttributes.srcSet = imgSrcSet
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}
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} else {
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imgAttributes = {
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'data-src': imgSrc,
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}
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if (imgSrcSet) {
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imgAttributes['data-srcset'] = imgSrcSet
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}
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className = className ? className + ' __lazy' : '__lazy'
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}
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let divStyle: React.CSSProperties | undefined
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let imgStyle: React.CSSProperties | undefined
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let wrapperStyle: React.CSSProperties | undefined
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if (
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typeof height !== 'undefined' &&
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typeof width !== 'undefined' &&
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!unsized
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) {
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// <Image src="i.png" width={100} height={100} />
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// <Image src="i.png" width="100" height="100" />
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const quotient =
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parseInt(height as string, 10) / parseInt(width as string, 10)
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const ratio = isNaN(quotient) ? 1 : quotient * 100
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wrapperStyle = {
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maxWidth: '100%',
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width,
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}
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divStyle = {
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position: 'relative',
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paddingBottom: `${ratio}%`,
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}
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imgStyle = {
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visibility: lazy ? 'hidden' : 'visible',
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height: '100%',
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left: '0',
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position: 'absolute',
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top: '0',
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width: '100%',
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}
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} else if (
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typeof height === 'undefined' &&
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typeof width === 'undefined' &&
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unsized
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) {
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// <Image src="i.png" unsized />
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if (process.env.NODE_ENV !== 'production') {
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if (priority) {
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// <Image src="i.png" unsized priority />
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console.warn(
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`Image with src "${src}" has both "priority" and "unsized" properties. Only one should be used.`
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)
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}
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}
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} else {
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// <Image src="i.png" />
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if (process.env.NODE_ENV !== 'production') {
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throw new Error(
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`Image with src "${src}" must use "width" and "height" properties or "unsized" property.`
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)
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}
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}
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// No need to add preloads on the client side--by the time the application is hydrated,
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// it's too late for preloads
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const shouldPreload = priority && typeof window === 'undefined'
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return (
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<div style={wrapperStyle}>
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<div style={divStyle}>
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{shouldPreload
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? generatePreload({
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src,
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widths: configSizes,
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unoptimized,
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sizes,
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quality,
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})
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: ''}
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<img
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{...rest}
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{...imgAttributes}
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className={className}
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sizes={sizes}
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ref={thisEl}
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style={imgStyle}
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/>
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</div>
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</div>
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)
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}
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//BUILT IN LOADERS
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type LoaderProps = CallLoaderProps & { root: string }
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function normalizeSrc(src: string) {
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return src[0] === '/' ? src.slice(1) : src
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}
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function imgixLoader({ root, src, width, quality }: LoaderProps): string {
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const params = ['auto=format', 'w=' + width]
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let paramsString = ''
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if (quality) {
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params.push('q=' + quality)
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}
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if (params.length) {
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paramsString = '?' + params.join('&')
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}
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return `${root}${normalizeSrc(src)}${paramsString}`
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}
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function akamaiLoader({ root, src, width }: LoaderProps): string {
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return `${root}${normalizeSrc(src)}?imwidth=${width}`
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}
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function cloudinaryLoader({ root, src, width, quality }: LoaderProps): string {
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const params = ['f_auto', 'w_' + width]
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let paramsString = ''
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if (quality) {
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params.push('q_' + quality)
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}
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if (params.length) {
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paramsString = params.join(',') + '/'
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}
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return `${root}${paramsString}${normalizeSrc(src)}`
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}
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function defaultLoader({ root, src, width, quality }: LoaderProps): string {
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return `${root}?url=${encodeURIComponent(src)}&w=${width}&q=${
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quality || '100'
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}`
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}
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