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Mini Shell
Mini Shell
class RocketPreloadLinks {
constructor( browser, config ) {
this.browser = browser;
this.config = config;
this.options = this.browser.options;
this.prefetched = new Set;
this.eventTime = null;
this.threshold = 1111;
this.numOnHover = 0;
}
/**
* Initializes the handler.
*/
init() {
if (
! this.browser.supportsLinkPrefetch()
||
this.browser.isDataSaverModeOn()
||
this.browser.isSlowConnection()
) {
return;
}
this.regex = {
excludeUris: RegExp( this.config.excludeUris, 'i' ),
images: RegExp( '.(' + this.config.imageExt + ')$', 'i' ),
fileExt: RegExp( '.(' + this.config.fileExt + ')$', 'i' )
};
this._initListeners( this );
}
/**
* Initializes the event listeners.
*
* @private
*
* @param self instance of this object, used for binding "this" to the listeners.
*/
_initListeners( self ) {
// Setting onHoverDelay to -1 disables the "on-hover" feature.
if ( this.config.onHoverDelay > -1 ) {
document.addEventListener( 'mouseover', self.listener.bind( self ), self.listenerOptions );
}
document.addEventListener( 'mousedown', self.listener.bind( self ), self.listenerOptions );
document.addEventListener( 'touchstart', self.listener.bind( self ), self.listenerOptions );
}
/**
* Event listener. Processes when near or on a valid <a> hyperlink.
*
* @param Event event Event instance.
*/
listener( event ) {
const linkElem = event.target.closest( 'a' );
const url = this._prepareUrl( linkElem );
if ( null === url ) {
return;
}
switch ( event.type ) {
case 'mousedown':
case 'touchstart':
this._addPrefetchLink( url );
break;
case 'mouseover':
this._earlyPrefetch( linkElem, url, 'mouseout' );
}
}
/**
*
* @private
*
* @param Element|null linkElem
* @param object url
* @param string resetEvent
*/
_earlyPrefetch( linkElem, url, resetEvent ) {
const doPrefetch = () => {
falseTrigger = null;
// Start the rate throttle: 1 sec timeout.
if ( 0 === this.numOnHover ) {
setTimeout( () => this.numOnHover = 0, 1000 );
}
// Bail out when exceeding the rate throttle.
else if ( this.numOnHover > this.config.rateThrottle ) {
return;
}
this.numOnHover++;
this._addPrefetchLink( url );
};
// Delay to avoid false triggers for hover/touch/tap.
let falseTrigger = setTimeout( doPrefetch, this.config.onHoverDelay );
// On reset event, reset the false trigger timer.
const reset = () => {
linkElem.removeEventListener( resetEvent, reset, { passive: true } );
if ( null === falseTrigger ) {
return;
}
clearTimeout( falseTrigger );
falseTrigger = null;
};
linkElem.addEventListener( resetEvent, reset, { passive: true } );
}
/**
* Adds a <link rel="prefetch" href="<url>"> for the given URL.
*
* @param string url The Given URL to prefetch.
*/
_addPrefetchLink( url ) {
this.prefetched.add( url.href );
return new Promise( ( resolve, reject ) => {
const elem = document.createElement( 'link' );
elem.rel = 'prefetch';
elem.href = url.href;
elem.onload = resolve;
elem.onerror = reject;
document.head.appendChild( elem );
} ).catch(() => {
// ignore and continue.
});
}
/**
* Prepares the target link's URL.
*
* @private
*
* @param Element|null linkElem Instance of the link element.
* @returns {null|*}
*/
_prepareUrl( linkElem ) {
if (
null === linkElem
||
typeof linkElem !== 'object'
||
! 'href' in linkElem
||
// Link prefetching only works on http/https protocol.
[ 'http:', 'https:' ].indexOf( linkElem.protocol ) === -1
) {
return null;
}
const origin = linkElem.href.substring( 0, this.config.siteUrl.length );
const pathname = this._getPathname( linkElem.href, origin );
const url = {
original: linkElem.href,
protocol: linkElem.protocol,
origin: origin,
pathname: pathname,
href: origin + pathname
};
return this._isLinkOk( url ) ? url : null;
}
/**
* Gets the URL's pathname. Note: ensures the pathname matches the permalink structure.
*
* @private
*
* @param object url Instance of the URL.
* @param string origin The target link href's origin.
* @returns {string}
*/
_getPathname( url, origin ) {
let pathname = origin
? url.substring( this.config.siteUrl.length )
: url;
if ( ! pathname.startsWith( '/' ) ) {
pathname = '/' + pathname;
}
if ( this._shouldAddTrailingSlash( pathname ) ) {
return pathname + '/';
}
return pathname;
}
_shouldAddTrailingSlash( pathname ) {
return (
this.config.usesTrailingSlash
&&
! pathname.endsWith( '/' )
&&
! this.regex.fileExt.test( pathname )
);
}
/**
* Checks if the given link element is okay to process.
*
* @private
*
* @param object url URL parts object.
*
* @returns {boolean}
*/
_isLinkOk( url ) {
if ( null === url || typeof url !== 'object' ) {
return false;
}
return (
! this.prefetched.has( url.href )
&&
url.origin === this.config.siteUrl // is an internal document.
&&
url.href.indexOf( '?' ) === -1 // not a query string.
&&
url.href.indexOf( '#' ) === -1 // not an anchor.
&&
! this.regex.excludeUris.test( url.href ) // not excluded.
&&
! this.regex.images.test( url.href ) // not an image.
);
}
/**
* Named static constructor to encapsulate how to create the object.
*/
static run() {
// Bail out if the configuration not passed from the server.
if ( typeof RocketPreloadLinksConfig === 'undefined' ) {
return;
}
const browser = new RocketBrowserCompatibilityChecker( {
capture: true,
passive: true
} );
const instance = new RocketPreloadLinks( browser, RocketPreloadLinksConfig );
instance.init();
}
}
RocketPreloadLinks.run();
Zerion Mini Shell 1.0