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diff --git a/files/zh-cn/web/javascript/reference/operators/assignment_operators/index.html b/files/zh-cn/web/javascript/reference/operators/assignment_operators/index.html deleted file mode 100644 index 66ae471cde..0000000000 --- a/files/zh-cn/web/javascript/reference/operators/assignment_operators/index.html +++ /dev/null @@ -1,413 +0,0 @@ ---- -title: 赋值运算符 -slug: Web/JavaScript/Reference/Operators/Assignment_Operators -tags: - - JavaScript - - 运算符 -translation_of: Web/JavaScript/Reference/Operators#Assignment_operators -translation_of_original: Web/JavaScript/Reference/Operators/Assignment_Operators ---- -<div>{{jsSidebar("Operators")}}</div> - -<p>赋值运算符（<strong>assignment operator</strong>）基于右值（right operand）的值，给左值（left operand）赋值。</p> - -<div>{{EmbedInteractiveExample("pages/js/expressions-assignment.html")}}</div> - -<p class="hidden">本文的交互示例的源代码存储在GithHub仓库。如果你愿意贡献更多交互示例，请克隆仓库 <a href="https://github.com/mdn/interactive-examples">https://github.com/mdn/interactive-examples</a> 并提交 pull request.</p> - -<h2 id="概述">概述</h2> - -<p>基本的赋值运算符是等号（<code>=</code>），该运算符把它右边的运算值赋给左边。即，<code>x = y</code> 把 <code>y</code> 的值赋给 <code>x</code>。 其他的赋值运算符通常是标准运算符的简写形式，如下面的定义与示例。 </p> - -<table class="standard-table"> - <tbody> - <tr> - <th>名称</th> - <th>简写形式</th> - <th>含义</th> - </tr> - <tr> - <td><a href="#Assignment">赋值（Assignment）</a></td> - <td><code>x = y</code></td> - <td><code>x = y</code></td> - </tr> - <tr> - <td><a href="#Addition_assignment">加赋值（Addition assignment）</a></td> - <td><code>x += y</code></td> - <td><code>x = x + y</code></td> - </tr> - <tr> - <td><a href="#Subtraction_assignment">减赋值（Subtraction assignment）</a></td> - <td><code>x -= y</code></td> - <td><code>x = x - y</code></td> - </tr> - <tr> - <td><a href="#Multiplication_assignment">乘赋值（Multiplication assigment）</a></td> - <td><code>x *= y</code></td> - <td><code>x = x * y</code></td> - </tr> - <tr> - <td><a href="#Division_assignment">除赋值（Division assignment）</a></td> - <td><code>x /= y</code></td> - <td><code>x = x / y</code></td> - </tr> - <tr> - <td><a href="#Remainder_assignment">模赋值（Remainder assignment）</a></td> - <td><code>x %= y</code></td> - <td><code>x = x % y</code></td> - </tr> - <tr> - <td><a href="#Exponentiation_assignment">指数赋值（Exponentiation assignment）</a></td> - <td><code>x **= y</code></td> - <td><code>x = x ** y</code></td> - </tr> - <tr> - <td><a href="#Left_shift_assignment">左移赋值（Left shift assignment）</a></td> - <td><code>x <<= y</code></td> - <td><code>x = x << y</code></td> - </tr> - <tr> - <td><a href="#Right_shift_assignment">右移赋值（Right shift assignment）</a></td> - <td><code>x >>= y</code></td> - <td><code>x = x >> y</code></td> - </tr> - <tr> - <td><a href="#Unsigned_right_shift_assignment">无符号右移赋值（Unsigned right shift assignment）</a></td> - <td><code>x >>>= y</code></td> - <td><code>x = x >>> y</code></td> - </tr> - <tr> - <td><a href="#Bitwise_AND_assignment">按位与赋值（Bitwise AND assignment）</a></td> - <td><code>x &= y</code></td> - <td><code>x = x & y</code></td> - </tr> - <tr> - <td><a href="#Bitwise_XOR_assignment">按位异或赋值（Bitwise XOR assignment）</a></td> - <td><code>x ^= y</code></td> - <td><code>x = x ^ y</code></td> - </tr> - <tr> - <td><a href="#Bitwise_OR_assignment">按位或赋值（Bitwise OR assignment）</a></td> - <td><code>x |= y</code></td> - <td><code>x = x | y</code></td> - </tr> - </tbody> -</table> - -<h2 id="赋值"><a name="Assignment">赋值</a></h2> - -<p>简单的赋值运算符，把一个值赋给一个变量。为了把一个值赋给多个变量，可以以链式使用赋值运算符。参考下例：</p> - -<h4 id="语法">语法</h4> - -<pre class="syntaxbox"><strong>Operator:</strong> x = y -</pre> - -<h4 id="示例">示例</h4> - -<pre class="brush: js">// Assuming the following variables -// x = 5 -// y = 10 -// z = 25 - -x = y // x is 10 -x = y = z // x, y and z are all 25 -</pre> - -<h3 id="加赋值（Addition_assignment）"><a name="Addition_assignment">加赋值（Addition assignment）</a></h3> - -<p>加赋值运算符把一个右值与一个变量相加，然后把相加的结果赋给该变量。两个操作数的类型决定了加赋值运算符的行为。算术相加或字符串连接都有可能。更多细节参考 {{jsxref("Operators/Arithmetic_Operators", "addition operator", "#Addition", 1)}}。</p> - -<h4 id="语法_2">语法</h4> - -<pre class="syntaxbox"><strong>Operator:</strong> x += y -<strong>Meaning:</strong> x = x + y -</pre> - -<h4 id="示例_2">示例</h4> - -<pre class="brush: js">// 定义下列变量 -// foo = 'foo' -// bar = 5 -// baz = true - - -// Number + Number -> addition -bar += 2 // 7 - -// Boolean + Number -> addition -baz += 1 // 2 - -// Boolean + Boolean -> addition -baz += false // 1 - -// Number + String -> concatenation -bar += 'foo' // "5foo" - -// String + Boolean -> concatenation -foo += false // "foofalse" - -// String + String -> concatenation -foo += 'bar' // "foobar" -</pre> - -<h3 id="减赋值（Subtraction_assignment）"><a name="Subtraction_assignment">减赋值（Subtraction assignment）</a></h3> - -<p>减赋值运算符使一个变量减去右值，然后把结果赋给该变量。更多细节查看 {{jsxref("Operators/Arithmetic_Operators", "subtraction operator", "#Subtraction", 1)}} 。</p> - -<h4 id="语法_3">语法</h4> - -<pre class="syntaxbox"><strong>Operator:</strong> x -= y -<strong>Meaning:</strong> x = x - y -</pre> - -<h4 id="示例_3">示例</h4> - -<pre class="brush: js">// 假定已定义了下面的变量 -// bar = 5 - -bar -= 2 // 3 -bar -= "foo" // NaN -</pre> - -<h3 id="乘赋值（Multiplication_assignment）"><a name="Multiplication_assignment">乘赋值（Multiplication assignment）</a></h3> - -<p>乘赋值运算符使一个变量乘以右值，然后把相成的结果赋给该变量。更多细节查看 {{jsxref("Operators/Arithmetic_Operators", "multiplication operator", "#Multiplication", 1)}}。</p> - -<h4 id="语法_4">语法</h4> - -<pre class="syntaxbox"><strong>Operator:</strong> x *= y -<strong>Meaning:</strong> x = x * y -</pre> - -<h4 id="示例_4">示例</h4> - -<pre class="brush: js">// 假定已定义了下面的变量 -// bar = 5 - -bar *= 2 // 10 -bar *= 'foo' // NaN -</pre> - -<h3 id="除赋值（Division_assignment）"><a name="Division_assignment">除赋值（Division assignment）</a></h3> - -<p>除赋值运算符使一个变量除以右值，然后把结果赋给该变量。更多细节查看 {{jsxref("Operators/Arithmetic_Operators", "division operator", "#Division", 1)}}。</p> - -<h4 id="语法_5">语法</h4> - -<pre class="syntaxbox"><strong>Operator:</strong> x /= y -<strong>Meaning:</strong> x = x / y -</pre> - -<h4 id="示例_5">示例</h4> - -<pre class="brush: js">// 假定已定义了下面的变量 -// bar = 5 - -bar /= 2 // 2.5 -bar /= "foo" // NaN -bar /= 0 // Infinity -</pre> - -<h3 id="模赋值（Remainder_assignment）"><a name="Remainder_assignment">模赋值（Remainder assignment）</a></h3> - -<p>模赋值运算符使一个变量除以右值，然后把余数赋给该变量。更多细节查看 {{jsxref("Operators/Arithmetic_Operators", "remainder operator", "#Remainder", 1)}}。</p> - -<h4 id="语法_6">语法</h4> - -<pre class="syntaxbox"><strong>Operator:</strong> x %= y -<strong>Meaning:</strong> x = x % y -</pre> - -<h4 id="示例_6">示例</h4> - -<pre class="brush: js">// Assuming the following variable -// bar = 5 - -bar %= 2 // 1 -bar %= 'foo' // NaN -bar %= 0 // NaN -</pre> - -<h3 id="指数赋值（Exponentiation_assignment）"><a id="Exponentiation_assignment" name="Exponentiation_assignment">指数赋值（Exponentiation assignment）</a></h3> - -<p>指数赋值运算符使一个变量为底数、以右值为指数的指数运算（乘方）结果赋给该变量。更多细节查看 {{jsxref("Operators/Arithmetic_Operators", "算术运算符", "#Exponentiation", 1)}}。</p> - -<h4 id="语法_7">语法</h4> - -<pre class="syntaxbox"><strong>语法:</strong> x **= y -<strong>含义:</strong> x = x ** y -</pre> - -<h4 id="示例_7">示例</h4> - -<pre class="brush: js">// Assuming the following variable -// bar = 5 - -bar **= 2 // 25 -bar **= 'foo' // NaN</pre> - -<h3 id="左移赋值（Left_shift_assignment）"><a name="Left_shift_assignment">左移赋值（Left shift assignment）</a></h3> - -<p>左移赋值运算符使变量向左移动指定位数的比特位，然后把结果赋给该变量。更多细节查看 {{jsxref("Operators/Bitwise_Operators", "left shift operator", "#Left_shift", 1)}}。</p> - -<h4 id="语法_8">语法</h4> - -<pre class="syntaxbox"><strong>Operator:</strong> x <<= y -<strong>Meaning:</strong> x = x << y -</pre> - -<h4 id="示例_8">示例</h4> - -<pre class="brush: js">var bar = 5; // (00000000000000000000000000000101) -bar <<= 2; // 20 (00000000000000000000000000010100) -</pre> - -<h3 id="右移赋值（Right_shift_assignment）"><a name="Right_shift_assignment">右移赋值（Right shift assignment）</a></h3> - -<p>右移赋值运算符使变量向右移指定位数的比特位，然后把结果赋给该变量。更多细节查看 {{jsxref("Operators/Bitwise_Operators", "right shift operator", "#Right_shift", 1)}}。</p> - -<h4 id="语法_9">语法</h4> - -<pre class="syntaxbox"><strong>Operator:</strong> x >>= y -<strong>Meaning:</strong> x = x >> y -</pre> - -<h4 id="示例_9">示例</h4> - -<pre class="brush: js">var bar = 5; // (00000000000000000000000000000101) -bar >>= 2; // 1 (00000000000000000000000000000001) - -var bar = -5; // (-00000000000000000000000000000101) -bar >>= 2; // -2 (-00000000000000000000000000000010) -</pre> - -<h3 id="无符号右移赋值（Unsigned_right_shift_assignment）"><a name="Unsigned_right_shift_assignment">无符号右移赋值（Unsigned right shift assignment）</a></h3> - -<p>无符号右移赋值运算符向右移动指定数量的比特位，然后把结果赋给变量。更多细节查看 {{jsxref("Operators/Bitwise_Operators", " unsigned right shift operator", "#Unsigned_right_shift", 1)}}。</p> - -<h4 id="语法_10">语法</h4> - -<pre class="syntaxbox"><strong>Operator:</strong> x >>>= y -<strong>Meaning:</strong> x = x >>> y -</pre> - -<h4 id="示例_10">示例</h4> - -<pre class="brush: js">var bar = 5; // (00000000000000000000000000000101) -bar >>>= 2; // 1 (00000000000000000000000000000001) - -var bar = -5; // (-00000000000000000000000000000101) -bar >>>= 2; // 1073741822 (00111111111111111111111111111110)</pre> - -<h3 id="按位与赋值（Bitwise_AND_assignment）"><a name="Bitwise_AND_assignment">按位与赋值（Bitwise AND assignment）</a></h3> - -<p>按位与赋值运算符使用两个操作值的二进制表示，执行按位与运算，并把结果赋给变量。更多细节查看 {{jsxref("Operators/Bitwise_Operators", "bitwise AND operator", "#Bitwise_AND", 1)}}。</p> - -<h4 id="语法_11">语法</h4> - -<pre class="syntaxbox"><strong>Operator:</strong> x &= y -<strong>Meaning:</strong> x = x & y -</pre> - -<h4 id="示例_11">示例</h4> - -<pre class="brush: js">var bar = 5; -// 5: 00000000000000000000000000000101 -// 2: 00000000000000000000000000000010 -bar &= 2; // 0 -</pre> - -<h3 id="按位异或赋值（Bitwise_XOR_assignment）"><a name="Bitwise_XOR_assignment">按位异或赋值（Bitwise XOR assignment）</a></h3> - -<p>按位异或赋值运算符使用两个操作值的二进制表示，执行二进制异或运算，并把结果赋给变量。更多细节查看 {{jsxref("Operators/Bitwise_Operators", "bitwise XOR operator", "#Bitwise_XOR", 1)}}。</p> - -<h4 id="语法_12">语法</h4> - -<pre class="syntaxbox"><strong>Operator:</strong> x ^= y -<strong>Meaning:</strong> x = x ^ y -</pre> - -<h4 id="示例_12">示例</h4> - -<pre class="brush: js">var bar = 5; -bar ^= 2; // 7 -// 5: 00000000000000000000000000000101 -// 2: 00000000000000000000000000000010 -// ----------------------------------- -// 7: 00000000000000000000000000000111 -</pre> - -<h3 id="按位或赋值（Bitwise_OR_assignment）"><a name="Bitwise_OR_assignment">按位或赋值（Bitwise OR assignment）</a></h3> - -<p>按位或赋值运算符使用两个操作值的二进制表示，执行按位或运算，并把结果赋给变量。更多细节查看 {{jsxref("Operators/Bitwise_Operators", "bitwise OR operator", "#Bitwise_OR", 1)}}。</p> - -<h4 id="语法_13">语法</h4> - -<pre class="syntaxbox"><strong>Operator:</strong> x |= y -<strong>Meaning:</strong> x = x | y -</pre> - -<h4 id="示例_13">示例</h4> - -<pre class="brush: js">var bar = 5; -bar |= 2; // 7 -// 5: 00000000000000000000000000000101 -// 2: 00000000000000000000000000000010 -// ----------------------------------- -// 7: 00000000000000000000000000000111 -</pre> - -<h2 id="示例_14">示例</h2> - -<h3 id="带有赋值运算符的左值（Left_operand）">带有赋值运算符的左值（Left operand）</h3> - -<p>在某些不常见的情况下，赋值运算符（如<code> x += y</code>）并不等同于表达式（ <code>x = x + y</code>）。当一个赋值运算符的左值包含有一个赋值运算符时，左值只会被求值一次。例如：</p> - -<pre class="brush: js">a[i++] += 5 // i 执行一次求值 -a[i++] = a[i++] + 5 // i 执行两次求值 -</pre> - -<h2 id="规范">规范</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('ESDraft', '#sec-assignment-operators', 'Assignment operators')}}</td> - <td>{{Spec2('ESDraft')}}</td> - <td></td> - </tr> - <tr> - <td>{{SpecName('ES2015', '#sec-assignment-operators', 'Assignment operators')}}</td> - <td>{{Spec2('ES2015')}}</td> - <td></td> - </tr> - <tr> - <td>{{SpecName('ES5.1', '#sec-11.13', 'Assignment operators')}}</td> - <td>{{Spec2('ES5.1')}}</td> - <td></td> - </tr> - <tr> - <td>{{SpecName('ES1', '#sec-11.13', 'Assignment operators')}}</td> - <td>{{Spec2('ES1')}}</td> - <td>Initial definition.</td> - </tr> - </tbody> -</table> - -<h2 id="浏览器兼容性">浏览器兼容性</h2> - -<div class="hidden">该兼容表是由结构化数据生成。如果你愿意贡献数据，请克隆仓库 <a href="https://github.com/mdn/browser-compat-data">https://github.com/mdn/browser-compat-data</a> 并提交 pull request.</div> - -<p>{{Compat("javascript.operators.assignment")}}</p> - -<h2 id="相关链接">相关链接</h2> - -<ul> - <li><a href="/zh-CN/docs/Web/JavaScript/Reference/Operators/Arithmetic_Operators">算术运算符</a></li> -</ul> |