---
title: allownegativeassertions
slug: Mozilla/Tech/XUL/Attribute/allownegativeassertions
translation_of: Archive/Mozilla/XUL/Attribute/allownegativeassertions
---
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 <dt><code id="a-allownegativeassertions"><a href="https://developer.mozilla.org/zh-CN/docs/Mozilla/Tech/XUL/Attribute/allownegativeassertions">allownegativeassertions</a></code></dt>
 <dd>Type: <em>boolean</em><br>
 类型：布尔类型</dd>
 <dd>Valid on any element that has a <code id="a-datasources"><a href="https://developer.mozilla.org/zh-CN/docs/Mozilla/Tech/XUL/Attribute/datasources">datasources</a></code> attribute. When multiple datasources are used, one may override an assertion from another. This attribute, if <code>true</code>, which is the default, allows a datasource to negate an earlier assertion.<br>
 适用于任何有 <code id="a-datasources"><a href="https://developer.mozilla.org/zh-CN/docs/Mozilla/Tech/XUL/Attribute/datasources">datasources</a></code> 属性的元素。当使用多个数据源，一个数据源可以指定覆盖另一个。这个属性，如果为真，这是默认值，允许一个数据源覆盖之前的数据源。</dd>
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