path: root/files/zh-cn/web/javascript/reference/global_objects/uint8clampedarray/index.html

---
title: Uint8ClampedArray
slug: Web/JavaScript/Reference/Global_Objects/Uint8ClampedArray
translation_of: Web/JavaScript/Reference/Global_Objects/Uint8ClampedArray
---
<div>{{JSRef}}</div>

<p><strong><code>Uint8ClampedArray</code>（8位无符号整型固定数组）</strong> 类型化数组表示一个由值固定在0-255区间的8位无符号整型组成的数组；如果你指定一个在 [0,255] 区间外的值，它将被替换为0或255；如果你指定一个非整数，那么它将被设置为最接近它的整数。（数组）内容被初始化为0。一旦（数组）被创建，你可以使用对象的方法引用数组里的元素，或使用标准的数组索引语法（即使用方括号标记）。</p>

<h2 id="语法">语法</h2>

<pre class="syntaxbox">new Uint8ClampedArray(length);
new Uint8ClampedArray(typedArray);
new Uint8ClampedArray(object);
new Uint8ClampedArray(buffer [, byteOffset [, length]]);</pre>

<p>关于构造函数语法和参数的更多信息，参见 <em><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray#Syntax">TypedArray</a></em>。</p>

<h2 id="属性">属性</h2>

<dl>
 <dt>{{jsxref("TypedArray.BYTES_PER_ELEMENT", "Uint8ClampedArray.BYTES_PER_ELEMENT")}}</dt>
 <dd>返回元素大小的一个数值。对 <code>Uint8ClampedArray</code> 而言是1。</dd>
 <dt>{{jsxref("TypedArray.prototype.length", "Uint8ClampedArray.prototype.length")}}</dt>
 <dd>静态长度属性值为0。对于实际长度（元素的数量），见 {{jsxref("TypedArray.prototype.length", "Uint8ClampedArray.prototype.length")}}。</dd>
 <dt>{{jsxref("TypedArray.name", "Uint8ClampedArray.name")}}</dt>
 <dd>返回构造函数名的字符串值。对 <code>Uint8ClampedArray</code> 类型而言："Uint8ClampedArray"。</dd>
 <dt>{{jsxref("TypedArray.prototype", "Uint8ClampedArray.prototype")}}</dt>
 <dd>原型是 <em>TypedArray</em> （类型化数组）对象。</dd>
</dl>

<h2 id="方法">方法</h2>

<dl>
 <dt>{{jsxref("TypedArray.from", "Uint8ClampedArray.from()")}}</dt>
 <dd>从一个类数组或可枚举对象创建一个新的 <code>Uint8ClampedArray</code>。参见 {{jsxref("Array.from()")}}。</dd>
 <dt>{{jsxref("TypedArray.of", "Uint8ClampedArray.of()")}}</dt>
 <dd>通过一个可选数量参数来创建一个新的 <code>Uint8ClampedArray</code>。参见 {{jsxref("Array.of()")}}。</dd>
</dl>

<h2 id="Uint8ClampedArray_原型">Uint8ClampedArray 原型</h2>

<p>所有的 <code>Uint8ClampedArray</code> 对象继承自 {{jsxref("TypedArray.prototype", "%TypedArray%.prototype")}}。</p>

<h3 id="属性_2">属性</h3>

<dl>
 <dt><code>Uint8ClampedArray.prototype.constructor</code></dt>
 <dd>返回创建一个实例原型的函数。这是 <code>Uint8ClampedArray</code> 默认的构造函数。</dd>
 <dt>{{jsxref("TypedArray.prototype.buffer", "Uint8ClampedArray.prototype.buffer")}} {{readonlyInline}}</dt>
 <dd>返回由 <code>Uint8ClampedArray</code> 引用的 {{jsxref("ArrayBuffer")}} 。在创建时所固定下来，因此<strong>只能读取</strong>。</dd>
 <dt>{{jsxref("TypedArray.prototype.byteLength", "Uint8ClampedArray.prototype.byteLength")}} {{readonlyInline}}</dt>
 <dd>返回从 {{jsxref("ArrayBuffer")}} 开始的 <code>Uint8ClampedArray</code> 的（字节的）长度。在创建时所固定下来，因此<strong>只能读取</strong>。</dd>
 <dt>{{jsxref("TypedArray.prototype.byteOffset", "Uint8ClampedArray.prototype.byteOffset")}} {{readonlyInline}}</dt>
 <dd>返回从 {{jsxref("ArrayBuffer")}} 开始的 <code>Uint8ClampedArray</code> 的（字节的）偏移。在创建时所固定下来，因此<strong>只能读取</strong>。</dd>
 <dt>{{jsxref("TypedArray.prototype.length", "Uint8ClampedArray.prototype.length")}} {{readonlyInline}}</dt>
 <dd>返回 <code>UintClamped8Array</code> 具有的元素数量。在创建时所固定下来，因此<strong>只能读取</strong>。</dd>
</dl>

<h3 id="方法_2">方法</h3>

<dl>
 <dt>{{jsxref("TypedArray.copyWithin", "Uint8ClampedArray.prototype.copyWithin()")}}</dt>
 <dd>复制数组内一段数组元素的序列。参见 {{jsxref("Array.prototype.copyWithin()")}}。</dd>
 <dt>{{jsxref("TypedArray.entries", "Uint8ClampedArray.prototype.entries()")}}</dt>
 <dd>返回一个新的包含数组中每个索引对应的键/值对的数组迭代器对象。参见 {{jsxref("Array.prototype.entries()")}}。</dd>
 <dt>{{jsxref("TypedArray.every", "Uint8ClampedArray.prototype.every()")}}</dt>
 <dd>测试数组里的所有元素是否通过所提供的函数的测试。参见 {{jsxref("Array.prototype.every()")}}。</dd>
 <dt>{{jsxref("TypedArray.fill", "Uint8ClampedArray.prototype.fill()")}}</dt>
 <dd>用一个固定值填充一个数组内的从起始索引到结束索引的全部元素。参见 {{jsxref("Array.prototype.fill()")}}。</dd>
 <dt>{{jsxref("TypedArray.filter", "Uint8ClampedArray.prototype.filter()")}}</dt>
 <dd>由该数组中所有经所提供的筛选函数返回为 true 的元素创建一个新数组。参见 {{jsxref("Array.prototype.filter()")}}。</dd>
 <dt>{{jsxref("TypedArray.find", "Uint8ClampedArray.prototype.find()")}}</dt>
 <dd>如果数组里的一个元素符合所提供的测试函数则返回找到的这个值，如果没有找到则返回 <code>undefined</code>。参见 {{jsxref("Array.prototype.find()")}}。</dd>
 <dt>{{jsxref("TypedArray.findIndex", "Uint8ClampedArray.prototype.findIndex()")}}</dt>
 <dd>如果数组里的一个元素符合所提供的测试函数则返回找到的索引，如果没有找到则返回 -1。参见 {{jsxref("Array.prototype.findIndex()")}}。</dd>
 <dt>{{jsxref("TypedArray.forEach", "Uint8ClampedArray.prototype.forEach()")}}</dt>
 <dd>对数组内的每个元素调用一个函数。参见 {{jsxref("Array.prototype.forEach()")}}。</dd>
 <dt>{{jsxref("TypedArray.includes", "Uint8ClampedArray.prototype.includes()")}} {{experimental_inline}}</dt>
 <dd>确定一个类型化数组是否包含一个特定的元素，对应地返回 <code>true</code> 或 <code>false</code>。参见 {{jsxref("Array.prototype.includes()")}}。</dd>
 <dt>{{jsxref("TypedArray.indexOf", "Uint8ClampedArray.prototype.indexOf()")}}</dt>
 <dd>Returns the first (least) index of an element within the array equal to the specified value, or -1 if none is found. See also {{jsxref("Array.prototype.indexOf()")}}.</dd>
 <dt>{{jsxref("TypedArray.join", "Uint8ClampedArray.prototype.join()")}}</dt>
 <dd>Joins all elements of an array into a string. See also {{jsxref("Array.prototype.join()")}}.</dd>
 <dt>{{jsxref("TypedArray.keys", "Uint8ClampedArray.prototype.keys()")}}</dt>
 <dd>Returns a new <code>Array Iterator</code> that contains the keys for each index in the array. See also {{jsxref("Array.prototype.keys()")}}.</dd>
 <dt>{{jsxref("TypedArray.lastIndexOf", "Uint8ClampedArray.prototype.lastIndexOf()")}}</dt>
 <dd>Returns the last (greatest) index of an element within the array equal to the specified value, or -1 if none is found. See also {{jsxref("Array.prototype.lastIndexOf()")}}.</dd>
 <dt>{{jsxref("TypedArray.map", "Uint8ClampedArray.prototype.map()")}}</dt>
 <dd>Creates a new array with the results of calling a provided function on every element in this array. See also {{jsxref("Array.prototype.map()")}}.</dd>
 <dt>{{jsxref("TypedArray.move", "Uint8ClampedArray.prototype.move()")}} {{non-standard_inline}} {{unimplemented_inline}}</dt>
 <dd>Former non-standard version of {{jsxref("TypedArray.copyWithin", "Uint8ClampedArray.prototype.copyWithin()")}}.</dd>
 <dt>{{jsxref("TypedArray.reduce", "Uint8ClampedArray.prototype.reduce()")}}</dt>
 <dd>Apply a function against an accumulator and each value of the array (from left-to-right) as to reduce it to a single value. See also {{jsxref("Array.prototype.reduce()")}}.</dd>
 <dt>{{jsxref("TypedArray.reduceRight", "Uint8ClampedArray.prototype.reduceRight()")}}</dt>
 <dd>Apply a function against an accumulator and each value of the array (from right-to-left) as to reduce it to a single value. See also {{jsxref("Array.prototype.reduceRight()")}}.</dd>
 <dt>{{jsxref("TypedArray.reverse", "Uint8ClampedArray.prototype.reverse()")}}</dt>
 <dd>Reverses the order of the elements of an array — the first becomes the last, and the last becomes the first. See also {{jsxref("Array.prototype.reverse()")}}.</dd>
 <dt>{{jsxref("TypedArray.set", "Uint8ClampedArray.prototype.set()")}}</dt>
 <dd>Stores multiple values in the typed array, reading input values from a specified array.</dd>
 <dt>{{jsxref("TypedArray.slice", "Uint8ClampedArray.prototype.slice()")}}</dt>
 <dd>Extracts a section of an array and returns a new array. See also {{jsxref("Array.prototype.slice()")}}.</dd>
 <dt>{{jsxref("TypedArray.some", "Uint8ClampedArray.prototype.some()")}}</dt>
 <dd>Returns true if at least one element in this array satisfies the provided testing function. See also {{jsxref("Array.prototype.some()")}}.</dd>
 <dt>{{jsxref("TypedArray.sort", "Uint8ClampedArray.prototype.sort()")}}</dt>
 <dd>Sorts the elements of an array in place and returns the array. See also {{jsxref("Array.prototype.sort()")}}.</dd>
 <dt>{{jsxref("TypedArray.subarray", "Uint8ClampedArray.prototype.subarray()")}}</dt>
 <dd>Returns a new <code>Uint8ClampedArray</code> from the given start and end element index.</dd>
 <dt>{{jsxref("TypedArray.values", "Uint8ClampedArray.prototype.values()")}}</dt>
 <dd>Returns a new <code>Array Iterator</code> object that contains the values for each index in the array. See also {{jsxref("Array.prototype.values()")}}.</dd>
 <dt>{{jsxref("TypedArray.toLocaleString", "Uint8ClampedArray.prototype.toLocaleString()")}}</dt>
 <dd>Returns a localized string representing the array and its elements. See also {{jsxref("Array.prototype.toLocaleString()")}}.</dd>
 <dt>{{jsxref("TypedArray.toString", "Uint8ClampedArray.prototype.toString()")}}</dt>
 <dd>Returns a string representing the array and its elements. See also {{jsxref("Array.prototype.toString()")}}.</dd>
 <dt>{{jsxref("TypedArray.@@iterator", "Uint8ClampedArray.prototype[@@iterator]()")}}</dt>
 <dd>Returns a new <code>Array Iterator</code> object that contains the values for each index in the array.</dd>
</dl>

<h2 id="实例">实例</h2>

<p>创建一个 <code>Uint8ClampedArray</code> 的不同方式：</p>

<pre class="brush: js">// From a length
var uintc8 = new Uint8ClampedArray(2);
uintc8[0] = 42;
uintc8[1] = 1337;
console.log(uintc8[0]); // 42
console.log(uintc8[1]); // 255 (clamped)
console.log(uintc8.length); // 2
console.log(uintc8.BYTES_PER_ELEMENT); // 1

// From an array
var arr = new Uint8ClampedArray([21,31]);
console.log(arr[1]); // 31

// From another TypedArray
var x = new Uint8ClampedArray([21, 31]);
var y = new Uint8ClampedArray(x);
console.log(y[0]); // 21

// From an ArrayBuffer
var buffer = new ArrayBuffer(8);
var z = new Uint8ClampedArray(buffer, 1, 4);

// From an iterable
var iterable = function*(){ yield* [1,2,3]; }();
var uintc8 = new Uint8ClampedArray(iterable);
// Uint8ClampedArray[1, 2, 3]
</pre>

<h2 id="规范">规范</h2>

<table class="standard-table">
 <tbody>
  <tr>
   <th scope="col">规范</th>
   <th scope="col">状态</th>
   <th scope="col">注释</th>
  </tr>
  <tr>
   <td>{{SpecName('Typed Array')}}</td>
   <td>{{Spec2('Typed Array')}}</td>
   <td>已由 ECMAScript 2015 替代。</td>
  </tr>
  <tr>
   <td>{{SpecName('ES6', '#table-49', 'TypedArray constructors')}}</td>
   <td>{{Spec2('ES6')}}</td>
   <td>最初定义在一份 ECMA 标准中。规定 <code>new</code> 是必需的。</td>
  </tr>
  <tr>
   <td>{{SpecName('ESDraft', '#table-49', 'TypedArray constructors')}}</td>
   <td>{{Spec2('ESDraft')}}</td>
   <td></td>
  </tr>
 </tbody>
</table>

<h2 id="浏览器兼容性">浏览器兼容性</h2>

<p>{{CompatibilityTable}}</p>

<div>
<table class="compat-table">
 <tbody>
  <tr>
   <th>特性</th>
   <th>Chrome</th>
   <th>Firefox (Gecko)</th>
   <th>Internet Explorer</th>
   <th>Opera</th>
   <th>Safari</th>
  </tr>
  <tr>
   <td>基础支持</td>
   <td>7.0</td>
   <td>{{ CompatGeckoDesktop(2) }}</td>
   <td>11 (as of <a href="https://support.microsoft.com/en-us/kb/2929437">KB2929437</a>)</td>
   <td>11.6</td>
   <td>5.1</td>
  </tr>
  <tr>
   <td>需要使用 <code>new</code></td>
   <td>{{CompatUnknown}}</td>
   <td>{{ CompatGeckoDesktop(44) }}</td>
   <td>{{CompatUnknown}}</td>
   <td>{{CompatUnknown}}</td>
   <td>{{CompatUnknown}}</td>
  </tr>
  <tr>
   <td>构造函数中可枚举</td>
   <td>{{CompatUnknown}}</td>
   <td>{{ CompatGeckoDesktop(52) }}</td>
   <td>{{CompatUnknown}}</td>
   <td>{{CompatUnknown}}</td>
   <td>{{CompatUnknown}}</td>
  </tr>
 </tbody>
</table>
</div>

<div>
<table class="compat-table">
 <tbody>
  <tr>
   <th>特性</th>
   <th>Android</th>
   <th>Chrome for Android</th>
   <th>Firefox Mobile (Gecko)</th>
   <th>IE Mobile</th>
   <th>Opera Mobile</th>
   <th>Safari Mobile</th>
  </tr>
  <tr>
   <td>基础支持</td>
   <td>4.0</td>
   <td>{{CompatVersionUnknown}}</td>
   <td>{{ CompatGeckoMobile(2) }}</td>
   <td>{{CompatVersionUnknown}}</td>
   <td>11.6</td>
   <td>4.2</td>
  </tr>
  <tr>
   <td>需要使用 <code>new</code></td>
   <td>{{CompatUnknown}}</td>
   <td>{{CompatUnknown}}</td>
   <td>{{ CompatGeckoMobile(44) }}</td>
   <td>{{CompatUnknown}}</td>
   <td>{{CompatUnknown}}</td>
   <td>{{CompatUnknown}}</td>
  </tr>
  <tr>
   <td>构造函数中可枚举</td>
   <td>{{CompatUnknown}}</td>
   <td>{{CompatUnknown}}</td>
   <td>{{ CompatGeckoMobile(52) }}</td>
   <td>{{CompatUnknown}}</td>
   <td>{{CompatUnknown}}</td>
   <td>{{CompatUnknown}}</td>
  </tr>
 </tbody>
</table>
</div>

<h2 id="兼容性注意事项">兼容性注意事项</h2>

<p>从 ECMAScript 2015 开始， <code>Uint8ClampedArray</code> 构造函数需要用一个 {{jsxref("Operators/new", "new")}} 操作符来构建。从现在开始，不使用 <code>new</code> 来调用一个 <code>Uint8ClampedArray</code> 构造函数将会抛出一个 {{jsxref("TypeError")}}。</p>

<pre class="brush: js example-bad">var dv = Uint8ClampedArray([1, 2, 3]);
// TypeError: calling a builtin Uint8ClampedArray constructor
// without new is forbidden</pre>

<pre class="brush: js example-good">var dv = new Uint8ClampedArray([1, 2, 3]);</pre>

<h2 id="参见">参见</h2>

<ul>
 <li><a href="/en-US/docs/Web/JavaScript/Typed_arrays">JavaScript typed arrays</a></li>
 <li>{{jsxref("ArrayBuffer")}}</li>
 <li>{{jsxref("DataView")}}</li>
</ul>