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diff --git a/files/zh-cn/web/javascript/reference/operators/operator_precedence/index.html b/files/zh-cn/web/javascript/reference/operators/operator_precedence/index.html new file mode 100644 index 0000000000..de411354aa --- /dev/null +++ b/files/zh-cn/web/javascript/reference/operators/operator_precedence/index.html @@ -0,0 +1,351 @@ +--- +title: 运算符优先级 +slug: Web/JavaScript/Reference/Operators/Operator_Precedence +tags: + - JavaScript + - 优先级 + - 运算符 +translation_of: Web/JavaScript/Reference/Operators/Operator_Precedence +--- +<div>{{jsSidebar("Operators")}}</div> + +<p><span class="st">运算符的优先级决定了表达式中运算执行的先后顺序</span>，优先级高的运算符最先被执行。</p> + +<div>{{EmbedInteractiveExample("pages/js/expressions-operatorprecedence.html")}}</div> + + + +<h2 id="Associativity" name="Associativity">关联性</h2> + +<p>关联性决定了拥有相同优先级的运算符的执行顺序。考虑下面这个表达式：</p> + +<pre class="notranslate">a OP b OP c; +</pre> + +<p>左关联（左到右）相当于把左边的子表达式加上小括号<code>(a OP b) OP c</code>，右关联（右到左）相当于<code>a OP (b OP c)</code>。赋值运算符是右关联的，所以你可以这么写：</p> + +<pre class="notranslate">a = b = 5; </pre> + +<p>结果 <code>a</code> 和 <code>b</code> 的值都会成为5。这是因为赋值运算符的返回结果就是赋值运算符右边的那个值，具体过程是：<code>b</code>被赋值为5，然后<code>a</code>也被赋值为 <code>b=5</code> 的返回值，也就是5。</p> + +<h2 id="示例">示例</h2> + +<pre class="brush: js notranslate">3 > 2 && 2 > 1 +// return true + +3 > 2 > 1 +// 返回 false，因为 3 > 2 是 true，并且 true > 1 is false +// 加括号可以更清楚：(3 > 2) > 1 +</pre> + +<h2 id="Table" name="Table">汇总表</h2> + +<p>下面的表将所有运算符按照优先级的不同从高（20）到低（1）排列。</p> + +<table class="fullwidth-table"> + <tbody> + <tr> + <th>优先级</th> + <th>运算类型</th> + <th>关联性</th> + <th>运算符</th> + </tr> + <tr> + <td>21</td> + <td>{{jsxref("Operators/Grouping", "圆括号")}}</td> + <td>n/a（不相关）</td> + <td><code>( … )</code></td> + </tr> + <tr> + <td rowspan="5">20</td> + <td>{{jsxref("Operators/Property_Accessors","成员访问", "#点符号表示法")}}</td> + <td>从左到右</td> + <td><code>… . …</code></td> + </tr> + <tr> + <td>{{jsxref("Operators/Property_Accessors","需计算的成员访问", "#括号表示法")}}</td> + <td>从左到右</td> + <td><code>… [ … ]</code></td> + </tr> + <tr> + <td>{{jsxref("Operators/new","new")}} (带参数列表)</td> + <td>n/a</td> + <td><code>new … ( … )</code></td> + </tr> + <tr> + <td><a href="https://developer.mozilla.org/zh-CN/docs/Web/JavaScript/Guide/Functions" title="JavaScript/Reference/Operators/Special_Operators/function_call">函数调用</a></td> + <td>从左到右</td> + <td><code>… ( <var>… </var>)</code></td> + </tr> + <tr> + <td><a href="https://developer.mozilla.org/zh-CN/docs/Web/JavaScript/Reference/Operators/Optional_chaining">可选链（Optional chaining）</a></td> + <td>从左到右</td> + <td><code>?.</code></td> + </tr> + <tr> + <td rowspan="1">19</td> + <td><a href="https://developer.mozilla.org/zh-CN/docs/Web/JavaScript/Reference/Operators/new" title="JavaScript/Reference/Operators/Special_Operators/new_Operator">new</a> (无参数列表)</td> + <td>从右到左</td> + <td><code>new …</code></td> + </tr> + <tr> + <td rowspan="2">18</td> + <td><a href="https://developer.mozilla.org/zh-CN/docs/Web/JavaScript/Reference/Operators/Arithmetic_Operators#Increment" title="JavaScript/Reference/Operators/Arithmetic_Operators">后置递增</a>(运算符在后)</td> + <td colspan="1" rowspan="2">n/a<br> + </td> + <td><code>… ++</code></td> + </tr> + <tr> + <td><a href="https://developer.mozilla.org/zh-CN/docs/Web/JavaScript/Reference/Operators/Arithmetic_Operators#Decrement" title="JavaScript/Reference/Operators/Arithmetic_Operators">后置递减</a>(运算符在后)</td> + <td><code>… --</code></td> + </tr> + <tr> + <td colspan="1" rowspan="10">17</td> + <td><a href="https://developer.mozilla.org/zh-CN/docs/Web/JavaScript/Reference/Operators/Logical_Operators#Logical_NOT">逻辑非</a></td> + <td colspan="1" rowspan="10">从右到左</td> + <td><code>! …</code></td> + </tr> + <tr> + <td><a href="https://developer.mozilla.org/zh-CN/docs/Web/JavaScript/Reference/Operators/Bitwise_Operators#Bitwise_NOT" title="JavaScript/Reference/Operators/Bitwise_Operators">按位非</a></td> + <td><code>~ …</code></td> + </tr> + <tr> + <td><a href="https://developer.mozilla.org/zh-CN/docs/Web/JavaScript/Reference/Operators/Arithmetic_Operators#Unary_plus" title="JavaScript/Reference/Operators/Arithmetic_Operators">一元加法</a></td> + <td><code>+ …</code></td> + </tr> + <tr> + <td><a href="https://developer.mozilla.org/zh-CN/docs/Web/JavaScript/Reference/Operators/Arithmetic_Operators#Unary_negation" title="JavaScript/Reference/Operators/Arithmetic_Operators">一元减法</a></td> + <td><code>- …</code></td> + </tr> + <tr> + <td><a href="https://developer.mozilla.org/zh-CN/docs/Web/JavaScript/Reference/Operators/Arithmetic_Operators#Increment" title="JavaScript/Reference/Operators/Arithmetic_Operators">前置递增</a></td> + <td><code>++ …</code></td> + </tr> + <tr> + <td><a href="https://developer.mozilla.org/zh-CN/docs/Web/JavaScript/Reference/Operators/Arithmetic_Operators#Decrement" title="JavaScript/Reference/Operators/Arithmetic_Operators">前置递减</a></td> + <td><code>-- …</code></td> + </tr> + <tr> + <td><a href="https://developer.mozilla.org/zh-CN/docs/Web/JavaScript/Reference/Operators/typeof" title="JavaScript/Reference/Operators/Special_Operators/typeof_Operator">typeof</a></td> + <td><code>typeof …</code></td> + </tr> + <tr> + <td><a href="https://developer.mozilla.org/zh-CN/docs/Web/JavaScript/Reference/Operators/void" title="JavaScript/Reference/Operators/Special_Operators/void_Operator">void</a></td> + <td><code>void …</code></td> + </tr> + <tr> + <td><a href="https://developer.mozilla.org/zh-CN/docs/Web/JavaScript/Reference/Operators/delete" title="JavaScript/Reference/Operators/Special_Operators/delete_Operator">delete</a></td> + <td><code>delete …</code></td> + </tr> + <tr> + <td><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/await">await</a></td> + <td><code>await …</code></td> + </tr> + <tr> + <td>16</td> + <td><a href="https://developer.mozilla.org/zh-CN/docs/Web/JavaScript/Reference/Operators/Arithmetic_Operators#Exponentiation" title="JavaScript/Reference/Operators/Arithmetic_Operators">幂</a></td> + <td>从右到左</td> + <td><code>… ** …</code></td> + </tr> + <tr> + <td rowspan="3">15</td> + <td><a href="https://developer.mozilla.org/zh-CN/docs/Web/JavaScript/Reference/Operators/Arithmetic_Operators#Multiplication" title="JavaScript/Reference/Operators/Arithmetic_Operators">乘法</a></td> + <td colspan="1" rowspan="3">从左到右<br> + </td> + <td><code>… * …</code></td> + </tr> + <tr> + <td><a href="https://developer.mozilla.org/zh-CN/docs/Web/JavaScript/Reference/Operators/Arithmetic_Operators#Division" title="JavaScript/Reference/Operators/Arithmetic_Operators">除法</a></td> + <td><code>… / …</code></td> + </tr> + <tr> + <td><a href="https://developer.mozilla.org/zh-CN/docs/Web/JavaScript/Reference/Operators/Arithmetic_Operators#Remainder" title="JavaScript/Reference/Operators/Arithmetic_Operators">取模</a></td> + <td><code>… % …</code></td> + </tr> + <tr> + <td rowspan="2">14</td> + <td><a href="https://developer.mozilla.org/zh-CN/docs/Web/JavaScript/Reference/Operators/Arithmetic_Operators#Addition" title="JavaScript/Reference/Operators/Arithmetic_Operators">加法</a></td> + <td colspan="1" rowspan="2">从左到右<br> + </td> + <td><code>… + …</code></td> + </tr> + <tr> + <td><a href="https://developer.mozilla.org/zh-CN/docs/Web/JavaScript/Reference/Operators/Arithmetic_Operators#Subtraction" title="JavaScript/Reference/Operators/Arithmetic_Operators">减法</a></td> + <td><code>… - …</code></td> + </tr> + <tr> + <td rowspan="3">13</td> + <td><a href="https://developer.mozilla.org/zh-CN/docs/Web/JavaScript/Reference/Operators/Bitwise_Operators" title="JavaScript/Reference/Operators/Bitwise_Operators">按位左移</a></td> + <td colspan="1" rowspan="3">从左到右</td> + <td><code>… << …</code></td> + </tr> + <tr> + <td><a href="https://developer.mozilla.org/zh-CN/docs/Web/JavaScript/Reference/Operators/Bitwise_Operators" title="JavaScript/Reference/Operators/Bitwise_Operators">按位右移</a></td> + <td><code>… >> …</code></td> + </tr> + <tr> + <td><a href="https://developer.mozilla.org/zh-CN/docs/Web/JavaScript/Reference/Operators/Bitwise_Operators" title="JavaScript/Reference/Operators/Bitwise_Operators">无符号右移</a></td> + <td><code>… >>> …</code></td> + </tr> + <tr> + <td rowspan="6">12</td> + <td><a href="https://developer.mozilla.org/zh-CN/docs/Web/JavaScript/Reference/Operators/Comparison_Operators#Less_than_operator" title="JavaScript/Reference/Operators/Comparison_Operators">小于</a></td> + <td colspan="1" rowspan="6">从左到右</td> + <td><code>… < …</code></td> + </tr> + <tr> + <td><a href="https://developer.mozilla.org/zh-CN/docs/Web/JavaScript/Reference/Operators/Comparison_Operators#Less_than__or_equal_operator" title="JavaScript/Reference/Operators/Comparison_Operators">小于等于</a></td> + <td><code>… <= …</code></td> + </tr> + <tr> + <td><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Comparison_Operators#Greater_than_operator" title="JavaScript/Reference/Operators/Comparison_Operators">大于</a></td> + <td><code>… > …</code></td> + </tr> + <tr> + <td><a href="https://developer.mozilla.org/zh-CN/docs/Web/JavaScript/Reference/Operators/Comparison_Operators#Greater_than_or_equal_operator" title="JavaScript/Reference/Operators/Comparison_Operators">大于等于</a></td> + <td><code>… >= …</code></td> + </tr> + <tr> + <td><a href="https://developer.mozilla.org/zh-CN/docs/Web/JavaScript/Reference/Operators/in" title="JavaScript/Reference/Operators/Special_Operators/in_Operator">in</a></td> + <td><code>… in …</code></td> + </tr> + <tr> + <td><a href="https://developer.mozilla.org/zh-CN/docs/Web/JavaScript/Reference/Operators/instanceof" title="JavaScript/Reference/Operators/Special_Operators/instanceof_Operator">instanceof</a></td> + <td><code>… instanceof …</code></td> + </tr> + <tr> + <td rowspan="4">11</td> + <td><a href="https://developer.mozilla.org/zh-CN/docs/Web/JavaScript/Reference/Operators/Comparison_Operators#Equality" title="JavaScript/Reference/Operators/Comparison_Operators">等号</a></td> + <td colspan="1" rowspan="4">从左到右<br> + </td> + <td><code>… == …</code></td> + </tr> + <tr> + <td><a href="https://developer.mozilla.org/zh-CN/docs/Web/JavaScript/Reference/Operators/Comparison_Operators#Inequality" title="JavaScript/Reference/Operators/Comparison_Operators">非等号</a></td> + <td><code>… != …</code></td> + </tr> + <tr> + <td><a href="https://developer.mozilla.org/zh-CN/docs/Web/JavaScript/Reference/Operators/Comparison_Operators#Identity" title="JavaScript/Reference/Operators/Comparison_Operators">全等号</a></td> + <td><code>… === …</code></td> + </tr> + <tr> + <td><a href="https://developer.mozilla.org/zh-CN/docs/Web/JavaScript/Reference/Operators/Comparison_Operators#Nonidentity" title="JavaScript/Reference/Operators/Comparison_Operators">非全等号</a></td> + <td><code>… !== …</code></td> + </tr> + <tr> + <td>10</td> + <td><a href="https://developer.mozilla.org/zh-CN/docs/Web/JavaScript/Reference/Operators/Bitwise_Operators#Bitwise_AND" title="JavaScript/Reference/Operators/Bitwise_Operators">按位与</a></td> + <td>从左到右</td> + <td><code>… & …</code></td> + </tr> + <tr> + <td>9</td> + <td><a href="https://developer.mozilla.org/zh-CN/docs/Web/JavaScript/Reference/Operators/Bitwise_Operators#Bitwise_XOR" title="JavaScript/Reference/Operators/Bitwise_Operators">按位异或</a></td> + <td>从左到右</td> + <td><code>… ^ …</code></td> + </tr> + <tr> + <td>8</td> + <td><a href="https://developer.mozilla.org/zh-CN/docs/Web/JavaScript/Reference/Operators/Bitwise_Operators#Bitwise_OR" title="JavaScript/Reference/Operators/Bitwise_Operators">按位或</a></td> + <td>从左到右</td> + <td><code>… | …</code></td> + </tr> + <tr> + <td>7</td> + <td><a href="https://developer.mozilla.org/zh-CN/docs/Web/JavaScript/Reference/Operators/Logical_Operators#Logical_AND" title="JavaScript/Reference/Operators/Logical_Operators">逻辑与</a></td> + <td>从左到右</td> + <td><code>… && …</code></td> + </tr> + <tr> + <td>6</td> + <td><a href="https://developer.mozilla.org/zh-CN/docs/Web/JavaScript/Reference/Operators/Logical_Operators#Logical_OR" title="JavaScript/Reference/Operators/Logical_Operators">逻辑或</a></td> + <td>从左到右</td> + <td><code>… || …</code></td> + </tr> + <tr> + <td>5</td> + <td><a href="https://developer.mozilla.org/zh-CN/docs/Web/JavaScript/Reference/Operators/Nullish_coalescing_operator" title="JavaScript/Reference/Operators/Nullish_coalescing_operator">空值合并</a></td> + <td>从左到右</td> + <td><code>… ?? …</code></td> + </tr> + <tr> + <td>4</td> + <td><a href="https://developer.mozilla.org/zh-CN/docs/Web/JavaScript/Reference/Operators/Conditional_Operator" title="JavaScript/Reference/Operators/Special_Operators/Conditional_Operator">条件运算符</a></td> + <td>从右到左</td> + <td><code>… ? … : …</code></td> + </tr> + <tr> + <td rowspan="16">3</td> + <td rowspan="16"><a href="https://developer.mozilla.org/zh-CN/docs/Web/JavaScript/Reference/Operators/Assignment_Operators" title="JavaScript/Reference/Operators/Assignment_Operators">赋值</a></td> + <td rowspan="16">从右到左</td> + <td><code>… = …</code></td> + </tr> + <tr> + <td><code>… += …</code></td> + </tr> + <tr> + <td><code>… -= …</code></td> + </tr> + <tr> + <td><code>… **= …</code></td> + </tr> + <tr> + <td><code>… *= …</code></td> + </tr> + <tr> + <td><code>… /= …</code></td> + </tr> + <tr> + <td><code>… %= …</code></td> + </tr> + <tr> + <td><code>… <<= …</code></td> + </tr> + <tr> + <td><code>… >>= …</code></td> + </tr> + <tr> + <td><code>… >>>= …</code></td> + </tr> + <tr> + <td><code>… &= …</code></td> + </tr> + <tr> + <td><code>… ^= …</code></td> + </tr> + <tr> + <td><code>… |= …</code></td> + </tr> + <tr> + <td><code>… &&= …</code></td> + </tr> + <tr> + <td><code>… ||= …</code></td> + </tr> + <tr> + <td><code>… ??= …</code></td> + </tr> + <tr> + <td colspan="1" rowspan="2">2</td> + <td><a href="https://developer.mozilla.org/zh-CN/docs/Web/JavaScript/Reference/Operators/yield" title="JavaScript/Reference/Operators/yield">yield</a></td> + <td colspan="1" rowspan="2">从右到左</td> + <td><code>yield …</code></td> + </tr> + <tr> + <td><a href="https://developer.mozilla.org/zh-CN/docs/Web/JavaScript/Reference/Operators/yield*" title="JavaScript/Reference/Operators/yield">yield*</a></td> + <td><code>yield* …</code></td> + </tr> + <tr> + <td>1</td> + <td><a href="https://developer.mozilla.org/zh-CN/docs/Web/JavaScript/Reference/Operators/Spread_operator" title="JavaScript/Reference/Operators/Spread_operator">展开运算符</a></td> + <td>n/a</td> + <td><code>...</code> …</td> + </tr> + <tr> + <td>0</td> + <td><a href="https://developer.mozilla.org/zh-CN/docs/Web/JavaScript/Reference/Operators/Comma_Operator" title="JavaScript/Reference/Operators/Comma_Operator">逗号</a></td> + <td>从左到右</td> + <td><code>… , …</code></td> + </tr> + </tbody> +</table> |