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| author | Peter Bengtsson <mail@peterbe.com> | 2020-12-08 14:40:17 -0500 |
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| committer | Peter Bengtsson <mail@peterbe.com> | 2020-12-08 14:40:17 -0500 |
| commit | 33058f2b292b3a581333bdfb21b8f671898c5060 (patch) | |
| tree | 51c3e392513ec574331b2d3f85c394445ea803c6 /files/zh-cn/web/javascript/reference/errors/equal_as_assign | |
| parent | 8b66d724f7caf0157093fb09cfec8fbd0c6ad50a (diff) | |
| download | translated-content-33058f2b292b3a581333bdfb21b8f671898c5060.tar.gz translated-content-33058f2b292b3a581333bdfb21b8f671898c5060.tar.bz2 translated-content-33058f2b292b3a581333bdfb21b8f671898c5060.zip | |
initial commit
Diffstat (limited to 'files/zh-cn/web/javascript/reference/errors/equal_as_assign')
| -rw-r--r-- | files/zh-cn/web/javascript/reference/errors/equal_as_assign/index.html | 52 |
1 files changed, 52 insertions, 0 deletions
diff --git a/files/zh-cn/web/javascript/reference/errors/equal_as_assign/index.html b/files/zh-cn/web/javascript/reference/errors/equal_as_assign/index.html new file mode 100644 index 0000000000..e92f0a63e8 --- /dev/null +++ b/files/zh-cn/web/javascript/reference/errors/equal_as_assign/index.html @@ -0,0 +1,52 @@ +--- +title: 'SyntaxError: test for equality (==) mistyped as assignment (=)?' +slug: Web/JavaScript/Reference/Errors/Equal_as_assign +tags: + - 语法错误 +translation_of: Web/JavaScript/Reference/Errors/Equal_as_assign +--- +<div>{{jsSidebar("Errors")}}</div> + +<h2 id="消息">消息</h2> + +<pre class="syntaxbox">Warning: SyntaxError: test for equality (==) mistyped as assignment (=)? +</pre> + +<h2 id="错误类型">错误类型</h2> + +<p>{{jsxref("SyntaxError")}} 只在<a href="/en-US/docs/Web/JavaScript/Reference/Strict_mode">严格模式</a>下会出现的警告。</p> + +<h2 id="什么地方出错了">什么地方出错了?</h2> + +<p>在通常期望进行相等判定(<code>==</code>)的地方出现了赋值<code>(=</code>)。 为了帮助调试,JavaScript(在开启严格模式的情况下)会对这种情况进行警告。</p> + +<h2 id="示例">示例</h2> + +<h3 id="条件表达式内的赋值">条件表达式内的赋值</h3> + +<p>不建议在条件表达式中 (例如 <code><a href="/en-US/docs/Web/JavaScript/Reference/Statements/if...else">if...else</a></code>) 使用简单赋值语句,因为在扫视代码的时候赋值操作与相等判定容易产生混淆。例如,不要使用以下写法:</p> + +<pre class="brush: js example-bad">if (x = y) { + // do the right thing +} +</pre> + +<p>如果你需要在条件表达式中使用赋值语句, 通常的做法是用一对括号把赋值语句包起来。 例如:</p> + +<pre class="brush: js">if ((x = y)) { + // do the right thing +}</pre> + +<p>否则, 你的本意可能是想用比较操作符 (如 <code>==</code> 或 <code>===</code>):</p> + +<pre class="brush: js">if (x == y) { + // do the right thing +}</pre> + +<h2 id="相关页面">相关页面</h2> + +<ul> + <li><a href="/en-US/docs/Web/JavaScript/Reference/Strict_mode">Strict mode</a></li> + <li><code><a href="/en-US/docs/Web/JavaScript/Reference/Statements/if...else">if...else</a></code></li> + <li><a href="/en-US/docs/Web/JavaScript/Reference/Operators/Comparison_Operators">Comparison operators</a></li> +</ul> |
