208 lines
10 KiB
Plaintext
Generated
208 lines
10 KiB
Plaintext
Generated
<!DOCTYPE html>
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<html>
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<meta charset="utf-8">
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<title>Go Em Exemplos: Switch</title>
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<link rel=stylesheet href="site.css">
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</head>
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<script>
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onkeydown = (e) => {
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if (e.key == "ArrowLeft") {
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window.location.href = 'if-else';
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}
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if (e.key == "ArrowRight") {
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window.location.href = 'arrays';
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}
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</script>
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<body>
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<div class="example" id="switch">
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<h2><a href="./">Go by Example</a>: Switch</h2>
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<table>
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<tr>
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<td class="docs">
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<p>Declarações <em>Switch</em> são geralmente utilizadas
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para condicionais com muitas ramificações.</p>
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</td>
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<td class="code empty leading">
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</td>
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</tr>
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<tr>
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<td class="docs">
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</td>
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<td class="code leading">
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<a target="_blank" href="https://go.dev/play/p/Y5mGHTuumK0"><img title="Executar código em nova aba" src="play.png" class="run" /></a><img title="Copiar código" src="clipboard.png" class="copy" />
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<pre class="chroma"><span class="kn">package</span> <span class="nx">main</span>
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</pre>
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</td>
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</tr>
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<tr>
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<td class="docs">
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</td>
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<td class="code leading">
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<pre class="chroma"><span class="kn">import</span> <span class="p">(</span>
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<span class="s">"fmt"</span>
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<span class="s">"time"</span>
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<span class="p">)</span>
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</pre>
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</td>
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</tr>
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<tr>
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<td class="docs">
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</td>
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<td class="code leading">
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<pre class="chroma"><span class="kd">func</span> <span class="nf">main</span><span class="p">()</span> <span class="p">{</span>
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</pre>
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</td>
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</tr>
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<tr>
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<td class="docs">
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<p>Aqui está um <code>switch</code> básico.</p>
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</td>
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<td class="code leading">
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<pre class="chroma">
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<span class="nx">i</span> <span class="o">:=</span> <span class="mi">2</span>
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<span class="nx">fmt</span><span class="p">.</span><span class="nf">Print</span><span class="p">(</span><span class="s">"Imprima "</span><span class="p">,</span> <span class="nx">i</span><span class="p">,</span> <span class="s">" como "</span><span class="p">)</span>
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<span class="k">switch</span> <span class="nx">i</span> <span class="p">{</span>
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<span class="k">case</span> <span class="mi">1</span><span class="p">:</span>
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<span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="s">"um"</span><span class="p">)</span>
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<span class="k">case</span> <span class="mi">2</span><span class="p">:</span>
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<span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="s">"dois"</span><span class="p">)</span>
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<span class="k">case</span> <span class="mi">3</span><span class="p">:</span>
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<span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="s">"três"</span><span class="p">)</span>
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<span class="p">}</span>
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</pre>
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</td>
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</tr>
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<tr>
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<td class="docs">
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<p>Vírgulas podem ser utilizadas para separar múltiplas
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expressões na mesma declaração <code>case</code>. A utilização
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de <code>default</code> é opcional.</p>
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</td>
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<td class="code leading">
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<pre class="chroma">
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<span class="k">switch</span> <span class="nx">time</span><span class="p">.</span><span class="nf">Now</span><span class="p">().</span><span class="nf">Weekday</span><span class="p">()</span> <span class="p">{</span>
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<span class="k">case</span> <span class="nx">time</span><span class="p">.</span><span class="nx">Saturday</span><span class="p">,</span> <span class="nx">time</span><span class="p">.</span><span class="nx">Sunday</span><span class="p">:</span>
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<span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="s">"É fim de semana"</span><span class="p">)</span>
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<span class="k">default</span><span class="p">:</span>
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<span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="s">"É dia de semana"</span><span class="p">)</span>
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<span class="p">}</span>
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</pre>
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</td>
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</tr>
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<tr>
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<td class="docs">
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<p><code>switch</code> sem nenhuma expressão é um meio alternativo
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para representar a lógica if/else. Aqui também é exibido como
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as expressões <code>case</code> podem ser não constantes.</p>
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</td>
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<td class="code leading">
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<pre class="chroma">
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<span class="nx">t</span> <span class="o">:=</span> <span class="nx">time</span><span class="p">.</span><span class="nf">Now</span><span class="p">()</span>
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<span class="k">switch</span> <span class="p">{</span>
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<span class="k">case</span> <span class="nx">t</span><span class="p">.</span><span class="nf">Hour</span><span class="p">()</span> <span class="p"><</span> <span class="mi">12</span><span class="p">:</span>
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<span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="s">"É antes do meio-dia"</span><span class="p">)</span>
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<span class="k">default</span><span class="p">:</span>
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<span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="s">"É depois do meio-dia"</span><span class="p">)</span>
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<span class="p">}</span>
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</pre>
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</td>
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</tr>
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<tr>
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<td class="docs">
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<p>Um <code>switch</code> de tipos compara tipos ao invés de valores.
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É possível utilizá-lo para descobrir o valor de um tipo
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interface. Neste exemplo, a variável <code>t</code> terá o tipo
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correspondente à sua cláusula.</p>
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</td>
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<td class="code">
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<pre class="chroma">
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<span class="nx">whatAmI</span> <span class="o">:=</span> <span class="kd">func</span><span class="p">(</span><span class="nx">i</span> <span class="kd">interface</span><span class="p">{})</span> <span class="p">{</span>
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<span class="k">switch</span> <span class="nx">t</span> <span class="o">:=</span> <span class="nx">i</span><span class="p">.(</span><span class="kd">type</span><span class="p">)</span> <span class="p">{</span>
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<span class="k">case</span> <span class="kt">bool</span><span class="p">:</span>
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<span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="s">"Sou um booleano"</span><span class="p">)</span>
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<span class="k">case</span> <span class="kt">int</span><span class="p">:</span>
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<span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="s">"Sou um inteiro"</span><span class="p">)</span>
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<span class="k">default</span><span class="p">:</span>
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<span class="nx">fmt</span><span class="p">.</span><span class="nf">Printf</span><span class="p">(</span><span class="s">"Não sei o meu tipo %T\n"</span><span class="p">,</span> <span class="nx">t</span><span class="p">)</span>
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<span class="p">}</span>
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<span class="p">}</span>
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<span class="nf">whatAmI</span><span class="p">(</span><span class="kc">true</span><span class="p">)</span>
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<span class="nf">whatAmI</span><span class="p">(</span><span class="mi">1</span><span class="p">)</span>
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<span class="nf">whatAmI</span><span class="p">(</span><span class="s">"hey"</span><span class="p">)</span>
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<span class="p">}</span>
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</pre>
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</td>
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</tr>
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</table>
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<table>
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<tr>
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<td class="docs">
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</td>
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<td class="code">
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<pre class="chroma"><span class="gp">$</span> go run switch.go
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<span class="go">Imprima 2 como dois
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</span><span class="go">É fim de semana
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</span><span class="go">É depois do meio-dia
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</span><span class="go">Sou um booleano
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</span><span class="go">Sou um inteiro
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</span><span class="go">Não sei o meu tipo string</span></pre>
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</td>
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</tr>
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</table>
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<p class="next">
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Próximo exemplo: <a href="arrays">Arrays</a>.
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</p>
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<p class="footer">
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Por <a href="https://markmcgranaghan.com">Mark McGranaghan</a> e <a href="https://eli.thegreenplace.net">Eli Bendersky</a> | traduzido por <a href="https://github.com/lucassauro">Lucassauro</a> | <a href="https://github.com/lucassauro/gobyexample">contribua</a> | <a href="https://github.com/mmcgrana/gobyexample#license">licença</a>
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</p>
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</div>
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<script>
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var codeLines = [];
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codeLines.push('');codeLines.push('package main\u000A');codeLines.push('import (\u000A \"fmt\"\u000A \"time\"\u000A)\u000A');codeLines.push('func main() {\u000A');codeLines.push(' i :\u003D 2\u000A fmt.Print(\"Imprima \", i, \" como \")\u000A switch i {\u000A case 1:\u000A fmt.Println(\"um\")\u000A case 2:\u000A fmt.Println(\"dois\")\u000A case 3:\u000A fmt.Println(\"três\")\u000A }\u000A');codeLines.push(' switch time.Now().Weekday() {\u000A case time.Saturday, time.Sunday:\u000A fmt.Println(\"É fim de semana\")\u000A default:\u000A fmt.Println(\"É dia de semana\")\u000A }\u000A');codeLines.push(' t :\u003D time.Now()\u000A switch {\u000A case t.Hour() \u003C 12:\u000A fmt.Println(\"É antes do meio-dia\")\u000A default:\u000A fmt.Println(\"É depois do meio-dia\")\u000A }\u000A');codeLines.push(' whatAmI :\u003D func(i interface{}) {\u000A switch t :\u003D i.(type) {\u000A case bool:\u000A fmt.Println(\"Sou um booleano\")\u000A case int:\u000A fmt.Println(\"Sou um inteiro\")\u000A default:\u000A fmt.Printf(\"Não sei o meu tipo %T\\n\", t)\u000A }\u000A }\u000A whatAmI(true)\u000A whatAmI(1)\u000A whatAmI(\"hey\")\u000A}\u000A');codeLines.push('');
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