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Paul O’Shannessy
592 lines
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HTML
592 lines
29 KiB
HTML
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<a href="/react/tips/introduction.html">Introduction</a>
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<a href="/react/tips/inline-styles.html">Inline Styles</a>
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<a href="/react/tips/maximum-number-of-jsx-root-nodes.html">Maximum Number of JSX Root Nodes</a>
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<li>
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<a href="/react/tips/style-props-value-px.html">Shorthand for Specifying Pixel Values in style props</a>
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<a href="/react/tips/children-props-type.html">Type of the Children props</a>
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<a href="/react/tips/controlled-input-null-value.html">Value of null for Controlled Input</a>
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<a href="/react/tips/componentWillReceiveProps-not-triggered-after-mounting.html">componentWillReceiveProps Not Triggered After Mounting</a>
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<a href="/react/tips/props-in-getInitialState-as-anti-pattern.html">Props in getInitialState Is an Anti-Pattern</a>
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</li>
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<li>
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<a href="/react/tips/dom-event-listeners.html">DOM Event Listeners in a Component</a>
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</li>
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<li>
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<a href="/react/tips/initial-ajax.html">Load Initial Data via AJAX</a>
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</li>
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<li>
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<a href="/react/tips/false-in-jsx.html">False in JSX</a>
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<li>
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<a href="/react/tips/communicate-between-components.html">Communicate Between Components</a>
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</li>
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<li>
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<a href="/react/tips/expose-component-functions.html">Expose Component Functions</a>
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</li>
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<li>
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<a href="/react/tips/children-undefined.html">this.props.children undefined</a>
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</li>
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<li>
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<a href="/react/tips/use-react-with-other-libraries.html">Use React with Other Libraries</a>
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</li>
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<li>
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<a href="/react/tips/dangerously-set-inner-html.html">Dangerously Set innerHTML</a>
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</li>
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</ul>
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</div>
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</div>
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<div class="inner-content">
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<h1>
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Terminologia del DOM (Virtuale)
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<a class="edit-page-link" href="https://github.com/facebook/react/tree/master/docs/docs/ref-10-glossary.it-IT.md" target="_blank">Edit on GitHub</a>
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</h1>
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<div class="subHeader"></div>
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<p>Nella terminologia di React, esistono cinque tipi base che è importante distinguere:</p>
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<ul>
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<li><a href="#react-elements">ReactElement / ReactElement Factory</a></li>
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<li><a href="#react-nodes">ReactNode</a></li>
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<li><a href="#react-components">ReactComponent / ReactComponent Class</a></li>
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</ul>
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<h2><a class="anchor" name="elementi-react"></a>Elementi React <a class="hash-link" href="#elementi-react">#</a></h2>
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<p>Il tipo primario in React è il <code>ReactElement</code>. Possiede quattro proprietà: <code>type</code>, <code>props</code>, <code>key</code> e <code>ref</code>. Non possiede alcun metodo e non espone nulla sul prototype.</p>
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<p>Puoi creare uno di questi oggetti attraverso <code>React.createElement</code>.</p>
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<div class="highlight"><pre><code class="language-javascript" data-lang="javascript"><span class="kd">var</span> <span class="nx">root</span> <span class="o">=</span> <span class="nx">React</span><span class="p">.</span><span class="nx">createElement</span><span class="p">(</span><span class="s1">'div'</span><span class="p">);</span>
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</code></pre></div>
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<p>Per effettuare il rendering di un nuovo albero nel DOM, crei dei <code>ReactElement</code> ande li passi a <code>ReactDOM.render</code> assieme a un <code>Element</code> DOM regolare (<code>HTMLElement</code> o <code>SVGElement</code>). I <code>ReactElement</code> non vanno confusi con gli <code>Element</code> del DOM. Un <code>ReactElement</code> è una rappresentazione leggera, priva di stato, immutabile e virtuale di un <code>Element</code> del DOM. È un DOM virtuale.</p>
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<div class="highlight"><pre><code class="language-javascript" data-lang="javascript"><span class="nx">ReactDOM</span><span class="p">.</span><span class="nx">render</span><span class="p">(</span><span class="nx">root</span><span class="p">,</span> <span class="nb">document</span><span class="p">.</span><span class="nx">getElementById</span><span class="p">(</span><span class="s1">'example'</span><span class="p">));</span>
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</code></pre></div>
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<p>Per aggiungere proprietà ad un elemento DOM, passa un oggetto di proprietà come secondo argomento, e i figli come terzo argomento.</p>
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<div class="highlight"><pre><code class="language-javascript" data-lang="javascript"><span class="kd">var</span> <span class="nx">child</span> <span class="o">=</span> <span class="nx">React</span><span class="p">.</span><span class="nx">createElement</span><span class="p">(</span><span class="s1">'li'</span><span class="p">,</span> <span class="kc">null</span><span class="p">,</span> <span class="s1">'Contenuto di Testo'</span><span class="p">);</span>
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<span class="kd">var</span> <span class="nx">root</span> <span class="o">=</span> <span class="nx">React</span><span class="p">.</span><span class="nx">createElement</span><span class="p">(</span><span class="s1">'ul'</span><span class="p">,</span> <span class="p">{</span> <span class="nx">className</span><span class="o">:</span> <span class="s1">'my-list'</span> <span class="p">},</span> <span class="nx">child</span><span class="p">);</span>
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<span class="nx">ReactDOM</span><span class="p">.</span><span class="nx">render</span><span class="p">(</span><span class="nx">root</span><span class="p">,</span> <span class="nb">document</span><span class="p">.</span><span class="nx">getElementById</span><span class="p">(</span><span class="s1">'example'</span><span class="p">));</span>
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</code></pre></div>
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<p>Se usi React JSX, allora questi <code>ReactElement</code> verranno creati per te. Questa espressione è equivalente:</p>
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<div class="highlight"><pre><code class="language-javascript" data-lang="javascript"><span class="kd">var</span> <span class="nx">root</span> <span class="o">=</span> <span class="o"><</span><span class="nx">ul</span> <span class="nx">className</span><span class="o">=</span><span class="s2">"my-list"</span><span class="o">></span>
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<span class="o"><</span><span class="nx">li</span><span class="o">></span><span class="nx">Contenuto</span> <span class="nx">di</span> <span class="nx">Testo</span><span class="o"><</span><span class="err">/li></span>
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<span class="o"><</span><span class="err">/ul>;</span>
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<span class="nx">ReactDOM</span><span class="p">.</span><span class="nx">render</span><span class="p">(</span><span class="nx">root</span><span class="p">,</span> <span class="nb">document</span><span class="p">.</span><span class="nx">getElementById</span><span class="p">(</span><span class="s1">'example'</span><span class="p">));</span>
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</code></pre></div><h3><a class="anchor" name="le-factory"></a>Le Factory <a class="hash-link" href="#le-factory">#</a></h3>
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<p>Una factory di <code>ReactElement</code> è semplicemente una funzione che genera un <code>ReactElement</code> con una particolare proprietà <code>type</code>. React ha uno helper integrato per permetterti di creare factory. La sua implementazione è semplicemente:</p>
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<div class="highlight"><pre><code class="language-javascript" data-lang="javascript"><span class="kd">function</span> <span class="nx">createFactory</span><span class="p">(</span><span class="nx">type</span><span class="p">)</span> <span class="p">{</span>
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<span class="k">return</span> <span class="nx">React</span><span class="p">.</span><span class="nx">createElement</span><span class="p">.</span><span class="nx">bind</span><span class="p">(</span><span class="kc">null</span><span class="p">,</span> <span class="nx">type</span><span class="p">);</span>
|
|
<span class="p">}</span>
|
|
</code></pre></div>
|
|
<p>Ti permette di creare una conveniente scorciatoia anziché scrivere ogni volta <code>React.createElement('div')</code>.</p>
|
|
<div class="highlight"><pre><code class="language-javascript" data-lang="javascript"><span class="kd">var</span> <span class="nx">div</span> <span class="o">=</span> <span class="nx">React</span><span class="p">.</span><span class="nx">createFactory</span><span class="p">(</span><span class="s1">'div'</span><span class="p">);</span>
|
|
<span class="kd">var</span> <span class="nx">root</span> <span class="o">=</span> <span class="nx">div</span><span class="p">({</span> <span class="nx">className</span><span class="o">:</span> <span class="s1">'my-div'</span> <span class="p">});</span>
|
|
<span class="nx">ReactDOM</span><span class="p">.</span><span class="nx">render</span><span class="p">(</span><span class="nx">root</span><span class="p">,</span> <span class="nb">document</span><span class="p">.</span><span class="nx">getElementById</span><span class="p">(</span><span class="s1">'example'</span><span class="p">));</span>
|
|
</code></pre></div>
|
|
<p>React possiede già factory integrate per tag HTML comuni:</p>
|
|
<div class="highlight"><pre><code class="language-javascript" data-lang="javascript"><span class="kd">var</span> <span class="nx">root</span> <span class="o">=</span> <span class="nx">React</span><span class="p">.</span><span class="nx">DOM</span><span class="p">.</span><span class="nx">ul</span><span class="p">({</span> <span class="nx">className</span><span class="o">:</span> <span class="s1">'my-list'</span> <span class="p">},</span>
|
|
<span class="nx">React</span><span class="p">.</span><span class="nx">DOM</span><span class="p">.</span><span class="nx">li</span><span class="p">(</span><span class="kc">null</span><span class="p">,</span> <span class="s1">'Contenuto di Testo'</span><span class="p">)</span>
|
|
<span class="p">);</span>
|
|
</code></pre></div>
|
|
<p>Se stai usando JSX non hai bisogno di factory. JSX fornisce già una conveniente scorciatoia per creare <code>ReactElement</code>.</p>
|
|
<h2><a class="anchor" name="nodi-react"></a>Nodi React <a class="hash-link" href="#nodi-react">#</a></h2>
|
|
<p>Un <code>ReactNode</code> può essere uno tra:</p>
|
|
|
|
<ul>
|
|
<li><code>ReactElement</code></li>
|
|
<li><code>string</code> (ovvero <code>ReactText</code>)</li>
|
|
<li><code>number</code> (ovvero <code>ReactText</code>)</li>
|
|
<li>Array di <code>ReactNode</code> (ovvero <code>ReactFragment</code>)</li>
|
|
</ul>
|
|
|
|
<p>Questi sono usati come proprietà di altri <code>ReactElement</code> per rappresentare i figli. Effettivamente creano un albero di <code>ReactElement</code>.</p>
|
|
<h2><a class="anchor" name="componenti-react"></a>Componenti React <a class="hash-link" href="#componenti-react">#</a></h2>
|
|
<p>Puoi usare React usando soltanto <code>ReactElement</code>, ma per avvantaggiarti seriamente di React vorrai usare i <code>ReactComponent</code> per creare incapsulamento con uno stato incluso.</p>
|
|
|
|
<p>Una classe <code>ReactComponent</code> è semplicemente una classe JavaScript (o una "funzione costruttore").</p>
|
|
<div class="highlight"><pre><code class="language-javascript" data-lang="javascript"><span class="kd">var</span> <span class="nx">MyComponent</span> <span class="o">=</span> <span class="nx">React</span><span class="p">.</span><span class="nx">createClass</span><span class="p">({</span>
|
|
<span class="nx">render</span><span class="o">:</span> <span class="kd">function</span><span class="p">()</span> <span class="p">{</span>
|
|
<span class="p">...</span>
|
|
<span class="p">}</span>
|
|
<span class="p">});</span>
|
|
</code></pre></div>
|
|
<p>Quando questo costruttore è invocato, ci si aspetta che restituisca un oggetto con almeno un metodo <code>render</code>. Questo oggetto è chiamato <code>ReactComponent</code>.</p>
|
|
<div class="highlight"><pre><code class="language-javascript" data-lang="javascript"><span class="kd">var</span> <span class="nx">component</span> <span class="o">=</span> <span class="k">new</span> <span class="nx">MyComponent</span><span class="p">(</span><span class="nx">props</span><span class="p">);</span> <span class="c1">// non farlo mai!</span>
|
|
</code></pre></div>
|
|
<p>Per scopi diversi dai test, <em>non chiamerai mai</em> questo costruttore direttamente. React lo chiamerà per te.</p>
|
|
|
|
<p>Invece, passa una classe <code>ReactComponent</code> a <code>createElement</code> per ottenere un <code>ReactElement</code>.</p>
|
|
<div class="highlight"><pre><code class="language-javascript" data-lang="javascript"><span class="kd">var</span> <span class="nx">element</span> <span class="o">=</span> <span class="nx">React</span><span class="p">.</span><span class="nx">createElement</span><span class="p">(</span><span class="nx">MyComponent</span><span class="p">);</span>
|
|
</code></pre></div>
|
|
<p>OPPURE usando JSX:</p>
|
|
<div class="highlight"><pre><code class="language-javascript" data-lang="javascript"><span class="kd">var</span> <span class="nx">element</span> <span class="o">=</span> <span class="o"><</span><span class="nx">MyComponent</span> <span class="o">/></span><span class="p">;</span>
|
|
</code></pre></div>
|
|
<p>Quando <code>element</code> viene passato a <code>ReactDOM.render</code>, React chiamerà il costruttore al tuo posto e creerà un<code>ReactComponent</code>, che verrà restituito.</p>
|
|
<div class="highlight"><pre><code class="language-javascript" data-lang="javascript"><span class="kd">var</span> <span class="nx">component</span> <span class="o">=</span> <span class="nx">ReactDOM</span><span class="p">.</span><span class="nx">render</span><span class="p">(</span><span class="nx">element</span><span class="p">,</span> <span class="nb">document</span><span class="p">.</span><span class="nx">getElementById</span><span class="p">(</span><span class="s1">'example'</span><span class="p">));</span>
|
|
</code></pre></div>
|
|
<p>Se chiami ripetutamente <code>ReactDOM.render</code> con lo stesso tipo di <code>ReactElement</code> e lo stesso <code>Element</code> DOM come contenitore, ti restituirà sempre la stessa istanza. Questa istanza è dotata di stato.</p>
|
|
<div class="highlight"><pre><code class="language-javascript" data-lang="javascript"><span class="kd">var</span> <span class="nx">componentA</span> <span class="o">=</span> <span class="nx">ReactDOM</span><span class="p">.</span><span class="nx">render</span><span class="p">(</span><span class="o"><</span><span class="nx">MyComponent</span> <span class="o">/></span><span class="p">,</span> <span class="nb">document</span><span class="p">.</span><span class="nx">getElementById</span><span class="p">(</span><span class="s1">'example'</span><span class="p">));</span>
|
|
<span class="kd">var</span> <span class="nx">componentB</span> <span class="o">=</span> <span class="nx">ReactDOM</span><span class="p">.</span><span class="nx">render</span><span class="p">(</span><span class="o"><</span><span class="nx">MyComponent</span> <span class="o">/></span><span class="p">,</span> <span class="nb">document</span><span class="p">.</span><span class="nx">getElementById</span><span class="p">(</span><span class="s1">'example'</span><span class="p">));</span>
|
|
<span class="nx">componentA</span> <span class="o">===</span> <span class="nx">componentB</span><span class="p">;</span> <span class="c1">// true</span>
|
|
</code></pre></div>
|
|
<p>Questo è il motivo per cui non dovresti mai costruire la tua istanza. Invece, <code>ReactElement</code> è un <code>ReactComponent</code> virtuale prima che venga costruito. Un vecchio <code>ReactElement</code> e uno nuovo possono essere confrontati per vedere se una nuova istanza di <code>ReactComponent</code> è stata creata o quella esistente è stata riutilizzata.</p>
|
|
|
|
<p>Ci si aspetta che il metodo <code>render</code> di un <code>ReactComponent</code> restituisca un altro <code>ReactElement</code>. Ciò permette a questi componenti di essere composti. In ultima analisi, il rendering si risolve in un <code>ReactElement</code> con un tag <code>string</code> che viene istanziato come un <code>Element</code> DOM e viene inserito nel documento.</p>
|
|
<h2><a class="anchor" name="definizioni-formali-dei-tipi"></a>Definizioni Formali dei Tipi <a class="hash-link" href="#definizioni-formali-dei-tipi">#</a></h2><h3><a class="anchor" name="punto-di-entrata"></a>Punto di Entrata <a class="hash-link" href="#punto-di-entrata">#</a></h3><div class="highlight"><pre><code class="language-text" data-lang="text">ReactDOM.render = (ReactElement, HTMLElement | SVGElement) => ReactComponent;
|
|
</code></pre></div><h3><a class="anchor" name="nodi-ed-elementi"></a>Nodi ed Elementi <a class="hash-link" href="#nodi-ed-elementi">#</a></h3><div class="highlight"><pre><code class="language-text" data-lang="text">type ReactNode = ReactElement | ReactFragment | ReactText;
|
|
|
|
type ReactElement = ReactComponentElement | ReactDOMElement;
|
|
|
|
type ReactDOMElement = {
|
|
type : string,
|
|
props : {
|
|
children : ReactNodeList,
|
|
className : string,
|
|
etc.
|
|
},
|
|
key : string | boolean | number | null,
|
|
ref : string | null
|
|
};
|
|
|
|
type ReactComponentElement<TProps> = {
|
|
type : ReactClass<TProps>,
|
|
props : TProps,
|
|
key : string | boolean | number | null,
|
|
ref : string | null
|
|
};
|
|
|
|
type ReactFragment = Array<ReactNode | ReactEmpty>;
|
|
|
|
type ReactNodeList = ReactNode | ReactEmpty;
|
|
|
|
type ReactText = string | number;
|
|
|
|
type ReactEmpty = null | undefined | boolean;
|
|
</code></pre></div><h3><a class="anchor" name="classi-e-componenti"></a>Classi e Componenti <a class="hash-link" href="#classi-e-componenti">#</a></h3><div class="highlight"><pre><code class="language-text" data-lang="text">type ReactClass<TProps> = (TProps) => ReactComponent<TProps>;
|
|
|
|
type ReactComponent<TProps> = {
|
|
props : TProps,
|
|
render : () => ReactElement
|
|
};
|
|
</code></pre></div>
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