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diff --git a/files/it/web/api/performance/now/index.html b/files/it/web/api/performance/now/index.html deleted file mode 100644 index 2331157f18..0000000000 --- a/files/it/web/api/performance/now/index.html +++ /dev/null @@ -1,104 +0,0 @@ ---- -title: performance.now() -slug: Web/API/Performance/now -tags: - - API - - Performance - - Prestazioni - - Reference - - Riferimento - - Web Performance API - - metodo -translation_of: Web/API/Performance/now ---- -<div>{{APIRef("High Resolution Timing")}}</div> - -<p>Il metodo <code><strong>performance.now()</strong></code> restituisce un {{domxref("DOMHighResTimeStamp")}}, misurato in millisecondi.</p> - -<div class="warning"> -<p>The timestamp is not actually high-resolution. To mitigate security threats such as <a href="https://spectreattack.com/">Spectre</a>, browsers currently round the results to varying degrees. (Firefox started rounding to 1 millisecond in Firefox 60.) Some browsers may also slightly randomize the timestamp. The precision may improve again in future releases; browser developers are still investigating these timing attacks and how best to mitigate them.</p> -</div> - -<p>{{AvailableInWorkers}}</p> - -<p>Il valore restituito rappresenta il tempo trascorso dal <a href="/en-US/docs/Web/API/DOMHighResTimeStamp#The_time_origin">time origin</a>.</p> - -<p>Tieni a mente i seguenti punti:</p> - -<ul> - <li>Negli workers dedicati creati da un contesto {{domxref("Window")}}, il valore nel worker sarà minore di <code>performance.now()</code> nella finestra che ha creato quel worker. Prima era lo stesso di <code>t0</code> nel contesto principale, ma è stato cambiato</li> - <li>Negli workers condivisi o di servizio, til valore nel worker potrebbe essere più alto di quello del contesto principale, perché quella finestra può essere creata dopo quegli workers.</li> -</ul> - -<h2 id="Sintassi">Sintassi</h2> - -<pre class="syntaxbox"><em>t</em> = performance.now();</pre> - -<h2 id="Esempio">Esempio</h2> - -<pre class="brush: js">var t0 = performance.now(); -doSomething(); -var t1 = performance.now(); -console.log("Call to doSomething took " + (t1 - t0) + " milliseconds."); -</pre> - -<p>A differenza di altri timing data disponibili con JavaScript (per esempio <a href="/en-US/docs/JavaScript/Reference/Global_Objects/Date/now"><code>Date.now</code></a>), i timestamps restituiti da <code>Performance.now()</code> non sono limitati a una risoluzione di un millisecondo. Invece, rappresentano il tempo come numeri a virgola mobile con una precisione che può arrivare a un microsecondo.</p> - -<p>Inolre, a differenza di <code>Date.now()</code>, il valore restituito da <code>Performance.now()</code> aumenta sempre con costanza, indipendentemente dal clock di sistema (che può essere regolato manualmente o distorto da software come NTP). Altrimenti, <code>performance.timing.navigationStart + performance.now()</code> sarà approssimativamente uguale a <code>Date.now()</code>.</p> - -<h2 id="Reduced_time_precision">Reduced time precision</h2> - -<p>To offer protection against timing attacks and fingerprinting, the precision of <code>performance.now()</code> might get rounded depending on browser settings.<br> - In Firefox, the <code>privacy.reduceTimerPrecision</code> preference is enabled by default and defaults to 1ms.</p> - -<pre class="brush: js">// reduced time precision (1ms) in Firefox 60 -performance.now(); -// 8781416 -// 8781815 -// 8782206 -// ... - - -// reduced time precision with `privacy.resistFingerprinting` enabled -performance.now(); -// 8865400 -// 8866200 -// 8866700 -// ... -</pre> - -<p>In Firefox, you can also enable <code>privacy.resistFingerprinting</code> — this changes the precision to 100ms or the value of <code>privacy.resistFingerprinting.reduceTimerPrecision.microseconds</code>, whichever is larger.</p> - -<h2 id="Specifications">Specifications</h2> - -<table class="standard-table"> - <tbody> - <tr> - <th scope="col">Specification</th> - <th scope="col">Status</th> - <th scope="col">Comment</th> - </tr> - <tr> - <td>{{SpecName('Highres Time Level 2', '#dom-performance-now', 'performance.now()')}}</td> - <td>{{Spec2('Highres Time Level 2')}}</td> - <td>Stricter definitions of interfaces and types.</td> - </tr> - <tr> - <td>{{SpecName('Highres Time', '#dom-performance-now', 'performance.now()')}}</td> - <td>{{Spec2('Highres Time')}}</td> - <td>Initial definition</td> - </tr> - </tbody> -</table> - -<h2 id="Browser_compatibility">Browser compatibility</h2> - - - -<p>{{Compat("api.Performance.now")}}</p> - -<h2 id="See_also">See also</h2> - -<ul> - <li><a href="http://updates.html5rocks.com/2012/08/When-milliseconds-are-not-enough-performance-now">When milliseconds are not enough: performance.now() </a>from HTML5 Rocks.</li> -</ul> |