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Paul O’Shannessy
317 lines
14 KiB
HTML
317 lines
14 KiB
HTML
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</div>
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<div class="inner-content">
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<h1>JSX Gotchas</h1>
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<div class="subHeader"></div>
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<p>JSX looks like HTML but there are some important differences you may run into.</p>
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<blockquote>
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<p>Note:</p>
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<p>For DOM differences, such as the inline <code>style</code> attribute, check <a href="dom-differences.html">here</a>.</p>
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</blockquote>
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<h2 id="whitespace-removal" class="anchor"><a href="#whitespace-removal">Whitespace Removal</a></h2>
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<p>JSX doesn't follow the same whitespace elimination rules as HTML. JSX removes all whitespace between two curly braces expressions. If you want to have whitespace, simply add <code>{' '}</code>.</p>
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<div class="highlight"><pre><code class="javascript language-javascript" data-lang="javascript"><span class="o"><</span><span class="nx">div</span><span class="o">></span><span class="p">{</span><span class="k">this</span><span class="p">.</span><span class="nx">props</span><span class="p">.</span><span class="nx">name</span><span class="p">}</span> <span class="p">{</span><span class="s1">' '</span><span class="p">}</span> <span class="p">{</span><span class="k">this</span><span class="p">.</span><span class="nx">props</span><span class="p">.</span><span class="nx">surname</span><span class="p">}</span><span class="o"><</span><span class="err">/div></span>
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</code></pre></div>
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<p>Follow <a href="https://github.com/facebook/react/issues/65">Issue #65</a> for discussion on this behavior.</p>
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<h2 id="html-entities" class="anchor"><a href="#html-entities">HTML Entities</a></h2>
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<p>You can insert HTML entities within literal text in JSX:</p>
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<div class="highlight"><pre><code class="javascript language-javascript" data-lang="javascript"><span class="o"><</span><span class="nx">div</span><span class="o">></span><span class="nx">First</span> <span class="o">&</span><span class="nx">middot</span><span class="p">;</span> <span class="nx">Second</span><span class="o"><</span><span class="err">/div></span>
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</code></pre></div>
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<p>If you want to display an HTML entity within dynamic content, you will run into double escaping issues as React escapes all the strings you are displaying in order to prevent a wide range of XSS attacks by default.</p>
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<div class="highlight"><pre><code class="javascript language-javascript" data-lang="javascript"><span class="c1">// Bad: It displays "First &middot; Second"</span>
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<span class="o"><</span><span class="nx">div</span><span class="o">></span><span class="p">{</span><span class="s1">'First &middot; Second'</span><span class="p">}</span><span class="o"><</span><span class="err">/div></span>
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</code></pre></div>
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<p>There are various ways to work-around this issue. The easiest one is to write unicode character directly in Javascript. You need to make sure that the file is saved as UTF-8 and that the proper UTF-8 directives are set so the browser will display it correctly.</p>
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<div class="highlight"><pre><code class="javascript language-javascript" data-lang="javascript"><span class="o"><</span><span class="nx">div</span><span class="o">></span><span class="p">{</span><span class="s1">'First · Second'</span><span class="p">}</span><span class="o"><</span><span class="err">/div></span>
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</code></pre></div>
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<p>A safer alternative is to find the <a href="http://www.fileformat.info/info/unicode/char/b7/index.htm">unicode number corresponding to the entity</a> and use it inside of a JavaScript string.</p>
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<div class="highlight"><pre><code class="javascript language-javascript" data-lang="javascript"><span class="o"><</span><span class="nx">div</span><span class="o">></span><span class="p">{</span><span class="s1">'First \u00b7 Second'</span><span class="p">}</span><span class="o"><</span><span class="err">/div></span>
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<span class="o"><</span><span class="nx">div</span><span class="o">></span><span class="p">{</span><span class="s1">'First '</span> <span class="o">+</span> <span class="nb">String</span><span class="p">.</span><span class="nx">fromCharCode</span><span class="p">(</span><span class="mi">183</span><span class="p">)</span> <span class="o">+</span> <span class="s1">' Second'</span><span class="p">}</span><span class="o"><</span><span class="err">/div></span>
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</code></pre></div>
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<p>You can use mixed arrays with strings and JSX elements.</p>
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<div class="highlight"><pre><code class="javascript language-javascript" data-lang="javascript"><span class="o"><</span><span class="nx">div</span><span class="o">></span><span class="p">{[</span><span class="s1">'First '</span><span class="p">,</span> <span class="o"><</span><span class="nx">span</span><span class="o">>&</span><span class="nx">middot</span><span class="p">;</span><span class="o"><</span><span class="err">/span>, ' Second']}</div></span>
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</code></pre></div>
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<p>As a last resort, you always have the ability to insert raw HTML.</p>
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<div class="highlight"><pre><code class="javascript language-javascript" data-lang="javascript"><span class="o"><</span><span class="nx">div</span> <span class="nx">dangerouslySetInnerHTML</span><span class="o">=</span><span class="p">{{</span><span class="nx">__html</span><span class="o">:</span> <span class="s1">'First &middot; Second'</span><span class="p">}}</span> <span class="o">/></span>
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</code></pre></div><h2 id="custom-html-attributes" class="anchor"><a href="#custom-html-attributes">Custom HTML Attributes</a></h2>
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<p>If you pass properties to native HTML elements that do not exist in the HTML specification, React will not render them. If you want to use a custom attribute, you should prefix it with <code>data-</code>.</p>
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<div class="highlight"><pre><code class="javascript language-javascript" data-lang="javascript"><span class="o"><</span><span class="nx">div</span> <span class="nx">data</span><span class="o">-</span><span class="nx">custom</span><span class="o">-</span><span class="nx">attribute</span><span class="o">=</span><span class="s2">"foo"</span> <span class="o">/></span>
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</code></pre></div>
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<p><a href="http://www.w3.org/WAI/intro/aria">Web Accessibility</a> attributes starting with <code>aria-</code> will be rendered properly.</p>
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<div class="highlight"><pre><code class="javascript language-javascript" data-lang="javascript"><span class="o"><</span><span class="nx">div</span> <span class="nx">aria</span><span class="o">-</span><span class="nx">hidden</span><span class="o">=</span><span class="p">{</span><span class="kc">true</span><span class="p">}</span> <span class="o">/></span>
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</code></pre></div>
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