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next.js/lib/page-loader.js

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/* global window, document, __NEXT_DATA__ */
import mitt from 'mitt'
const webpackModule = module
export default class PageLoader {
constructor (buildId, assetPrefix) {
this.buildId = buildId
this.assetPrefix = assetPrefix
this.pageCache = {}
this.pageLoadedHandlers = {}
this.pageRegisterEvents = mitt()
this.loadingRoutes = {}
this.chunkRegisterEvents = mitt()
this.loadedChunks = {}
}
normalizeRoute (route) {
if (route[0] !== '/') {
throw new Error(`Route name should start with a "/", got "${route}"`)
}
route = route.replace(/index$/, '')
if (route === '/') return route
return route.replace(/\/$/, '')
}
loadPage (route) {
route = this.normalizeRoute(route)
const cachedPage = this.pageCache[route]
if (cachedPage) {
return new Promise((resolve, reject) => {
if (cachedPage.error) return reject(cachedPage.error)
return resolve(cachedPage.page)
})
}
return new Promise((resolve, reject) => {
const fire = ({ error, page }) => {
this.pageRegisterEvents.off(route, fire)
if (error) {
reject(error)
} else {
resolve(page)
}
}
this.pageRegisterEvents.on(route, fire)
// If the page is loading via SSR, we need to wait for it
// rather downloading it again.
if (document.getElementById(`__NEXT_PAGE__${route}`)) {
return
}
// Load the script if not asked to load yet.
if (!this.loadingRoutes[route]) {
this.loadScript(route)
this.loadingRoutes[route] = true
}
})
}
loadScript (route) {
route = this.normalizeRoute(route)
if (__NEXT_DATA__.nextExport) {
route = route === '/' ? '/index.js' : `${route}/index.js`
}
const script = document.createElement('script')
const url = `${this.assetPrefix}/_next/${encodeURIComponent(this.buildId)}/page${route}`
script.src = url
script.type = 'text/javascript'
script.onerror = () => {
const error = new Error(`Error when loading route: ${route}`)
this.pageRegisterEvents.emit(route, { error })
}
document.body.appendChild(script)
}
// This method if called by the route code.
registerPage (route, regFn) {
const register = () => {
try {
const { error, page } = regFn()
this.pageCache[route] = { error, page }
this.pageRegisterEvents.emit(route, { error, page })
} catch (error) {
this.pageCache[route] = { error }
this.pageRegisterEvents.emit(route, { error })
}
}
// Wait for webpack to became idle if it's not.
// More info: https://github.com/zeit/next.js/pull/1511
if (webpackModule && webpackModule.hot && webpackModule.hot.status() !== 'idle') {
console.log(`Waiting webpack to became "idle" to initialize the page: "${route}"`)
const check = (status) => {
if (status === 'idle') {
webpackModule.hot.removeStatusHandler(check)
register()
}
}
webpackModule.hot.status(check)
} else {
register()
}
}
registerChunk (chunkName, regFn) {
const chunk = regFn()
this.loadedChunks[chunkName] = true
this.chunkRegisterEvents.emit(chunkName, chunk)
}
waitForChunk (chunkName, regFn) {
const loadedChunk = this.loadedChunks[chunkName]
if (loadedChunk) {
return Promise.resolve(true)
}
return new Promise((resolve) => {
const register = (chunk) => {
this.chunkRegisterEvents.off(chunkName, register)
resolve(chunk)
}
this.chunkRegisterEvents.on(chunkName, register)
})
}
clearCache (route) {
route = this.normalizeRoute(route)
delete this.pageCache[route]
delete this.loadingRoutes[route]
const script = document.getElementById(`__NEXT_PAGE__${route}`)
if (script) {
script.parentNode.removeChild(script)
}
}
}