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---
title: PerformanceEntry.toJSON()
slug: Web/API/PerformanceEntry/toJSON
tags:
- PerformanceEntry.toJSON()
translation_of: Web/API/PerformanceEntry/toJSON
---
<div>{{APIRef("Performance Timeline API")}}</div>
<p><strong><code>toJSON()</code></strong> 方法是一个串行器( <em>serializer </em>); 它返回{{domxref("PerformanceEntry","performance entry")}}对象的一个JSON表示形式。</p>
<h2 id="Syntax">Syntax</h2>
<pre class="syntaxbox">const json = perfEntry.toJSON();
</pre>
<h3 id="Arguments">Arguments</h3>
<dl>
<dt>None</dt>
<dd> </dd>
</dl>
<h3 id="Return_value">Return value</h3>
<dl>
<dt>json</dt>
<dd>A JSON object that is the serialization of the {{domxref("PerformanceEntry")}} object.</dd>
</dl>
<h2 id="Example">Example</h2>
<p>The following example shows the use of the <code>toJSON()</code> method.</p>
<pre class="brush: js">function run_PerformanceEntry() {
log("PerformanceEntry support ...");
if (performance.mark === undefined) {
log("... performance.mark Not supported");
return;
}
// Create some performance entries via the mark() method
performance.mark("Begin");
do_work(50000);
performance.mark("End");
// Use getEntries() to iterate through the each entry
var p = performance.getEntries();
for (var i=0; i < p.length; i++) {
log("Entry[" + i + "]");
check_PerformanceEntry(p[i]);
}
}
function check_PerformanceEntry(obj) {
var properties = ["name", "entryType", "startTime", "duration"];
var methods = ["toJSON"];
for (var i=0; i < properties.length; i++) {
// check each property
var supported = properties[i] in obj;
if (supported)
log("..." + properties[i] + " = " + obj[properties[i]]);
else
log("..." + properties[i] + " = Not supported");
}
for (var i=0; i < methods.length; i++) {
// check each method
var supported = typeof obj[methods[i]] == "function";
if (supported) {
var js = obj[methods[i]]();
log("..." + methods[i] + "() = " + JSON.stringify(js));
} else {
log("..." + methods[i] + " = Not supported");
}
}
}
</pre>
<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('Performance Timeline Level 2', '#dom-performanceentry', 'toJSON')}}</td>
<td>{{Spec2('Performance Timeline Level 2')}}</td>
<td>Initial definition of <code>toJSON()</code> method.</td>
</tr>
</tbody>
</table>
<h2 id="Browser_compatibility">Browser compatibility</h2>
<div>
<div>
<p>{{Compat("api.PerformanceEntry.toJSON")}}</p>
</div>
</div>
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