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---
title: PerformanceResourceTiming.domainLookupStart
slug: Web/API/PerformanceResourceTiming/domainLookupStart
tags:
- API
- Web パフォーマンス
- プロパティ
- リファレンス
translation_of: Web/API/PerformanceResourceTiming/domainLookupStart
---
<div>{{APIRef("Resource Timing API")}}</div>
<p><strong><code>domainLookupStart</code></strong> 読み取り専用プロパティは、ブラウザがリソースのドメイン名検索を開始する直前に {{domxref("DOMHighResTimeStamp","timestamp")}} を返します。</p>
<p>{{AvailableInWorkers}}</p>
<h2 id="Syntax" name="Syntax">構文</h2>
<pre class="syntaxbox"><em>resource</em>.domainLookupStart;
</pre>
<h3 id="Return_Value" name="Return_Value">戻り値</h3>
<p>ブラウザがリソースのドメイン名検索を開始する直前の {{domxref("DOMHighResTimeStamp")}}。</p>
<h2 id="例">例</h2>
<p>次の例では、すべての "<code>resource</code>" {{domxref("PerformanceEntry.entryType","type")}} イベントの <code>*Start</code> プロパティと <code>*End</code> プロパティの値が記録されます。</p>
<pre class="brush: js">function print_PerformanceEntries() {
// Use getEntriesByType() to just get the "resource" events
var p = performance.getEntriesByType("resource");
for (var i=0; i < p.length; i++) {
print_start_and_end_properties(p[i]);
}
}
function print_start_and_end_properties(perfEntry) {
// Print timestamps of the PerformanceEntry *start and *end properties
properties = ["connectStart", "connectEnd",
"domainLookupStart", "domainLookupEnd",
"fetchStart",
"redirectStart", "redirectEnd",
"requestStart",
"responseStart", "responseEnd",
"secureConnectionStart"];
for (var i=0; i < properties.length; i++) {
// check each property
var supported = properties[i] in perfEntry;
if (supported) {
var value = perfEntry[properties[i]];
console.log("... " + properties[i] + " = " + value);
} else {
console.log("... " + properties[i] + " = NOT supported");
}
}
}
</pre>
<h2 id="仕様">仕様</h2>
<table class="standard-table">
<tbody>
<tr>
<th scope="col">仕様書</th>
<th scope="col">ステータス</th>
<th scope="col">コメント</th>
</tr>
<tr>
<td>{{SpecName('Resource Timing', '#widl-PerformanceResourceTiming-domainLookupStart', 'domainLookupStart')}}</td>
<td>{{Spec2('Resource Timing')}}</td>
<td>初期定義</td>
</tr>
</tbody>
</table>
<h2 id="ブラウザの互換性">ブラウザの互換性</h2>
<p>{{Compat("api.PerformanceResourceTiming.domainLookupStart")}}</p>
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