Fashion
2021-12-02
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Mark Willy
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![<blockquote>The slice() method returns a shallow copy of a portion of an array into a new array object selected from start to end (end not included) where start and end represent the index of items in that array. The original array will not be modified.</blockquote><h3>1. Создадим массив из массива начиная с n позиции в массиве. Например, мы хотим начать использовать список с 3 элемента</h3><pre class="ql-syntax" spellcheck="false"><span class="hljs-keyword">const</span> animals = [<span class="hljs-string">'ant'</span>, <span class="hljs-string">'bison'</span>, <span class="hljs-string">'camel'</span>, <span class="hljs-string">'duck'</span>, <span class="hljs-string">'elephant'</span>];
<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(animals.<span class="hljs-title function_">slice</span>(<span class="hljs-number">2</span>));
<span class="hljs-comment">// expected output: Array ["camel", "duck", "elephant"]</span>
</pre><p><span class="hljs-comment">Или, например, мы хотим взять последние 2 элемента из списка</span></p><pre class="ql-syntax" spellcheck="false"><span class="hljs-keyword">const</span> animals = [<span class="hljs-string">'ant'</span>, <span class="hljs-string">'bison'</span>, <span class="hljs-string">'camel'</span>, <span class="hljs-string">'duck'</span>, <span class="hljs-string">'elephant'</span>];
<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(animals.<span class="hljs-title function_">slice</span>(-<span class="hljs-number">2</span>));
<span class="hljs-comment">// expected output: Array ["duck", "elephant"]</span>
</pre><h3>2. Клонирование массива. Иногда нужно получить копию массива без ссылок, просто используем slice без аргументов</h3><pre class="ql-syntax" spellcheck="false">const animals = [<span class="hljs-string">'ant'</span>, <span class="hljs-string">'bison'</span>, <span class="hljs-string">'camel'</span>, <span class="hljs-string">'duck'</span>, <span class="hljs-string">'elephant'</span>];
console.log(animals.<span class="hljs-built_in">slice</span>());
// expected output: Array [<span class="hljs-string">'ant'</span>, <span class="hljs-string">'bison'</span>, <span class="hljs-string">'camel'</span>, <span class="hljs-string">'duck'</span>, <span class="hljs-string">'elephant'</span>]
</pre><p>Изменения в копии не приведут в изменении в основном массиве</p><h3>3. Преобразования массиво-подобных объектов в массив</h3><pre class="ql-syntax" spellcheck="false"><span class="hljs-keyword">function</span> <span class="hljs-title function_">argToArray</span>(){
<span class="hljs-keyword">return</span> <span class="hljs-title class_">Array</span>.<span class="hljs-property"><span class="hljs-keyword">prototype</span></span>.<span class="hljs-property">slice</span>.<span class="hljs-title function_">call</span>(<span class="hljs-variable language_">arguments</span>);
}
<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-title function_">aargToArray</span>(<span class="hljs-string">"1"</span>, <span class="hljs-string">"2"</span>, <span class="hljs-string">"3"</span>, <span class="hljs-string">"4"</span>));
<span class="hljs-comment">// expected output: Array ["1", "2", "3", "4"]</span>
</pre><h3>4. Преобразовать NodeList из DOM в массив</h3><pre class="ql-syntax" spellcheck="false"><span class="hljs-keyword">const</span> allDiv = <span class="hljs-variable language_">document</span>.<span class="hljs-title function_">querySelectorAll</span>(‘div’);
<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-title class_">Array</span>.<span class="hljs-property"><span class="hljs-keyword">prototype</span></span>.<span class="hljs-property">slice</span>.<span class="hljs-title function_">call</span>(allDiv));
</pre><p>expected output:</p><p><img src="/uploads/brochures/post_inner/image-61961587bd57c.png"></p><h3>5. Заменить элемент в строке по индексу</h3><pre class="ql-syntax" spellcheck="false"><span class="hljs-title class_">String</span>.<span class="hljs-property"><span class="hljs-keyword">prototype</span></span>.<span class="hljs-property">append</span> = <span class="hljs-keyword">function</span> (<span class="hljs-params">index,value</span>) {
<span class="hljs-keyword">return</span> <span class="hljs-variable language_">this</span>.<span class="hljs-title function_">slice</span>(<span class="hljs-number">0</span>,index) + value + <span class="hljs-variable language_">this</span>.<span class="hljs-title function_">slice</span>(index);
};
<span class="hljs-keyword">const</span> person = <span class="hljs-string">"Captain Sparrow"</span>;
<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(person.<span class="hljs-title function_">append</span>(<span class="hljs-number">8</span>,<span class="hljs-string">"Jack "</span>));
expected <span class="hljs-attr">output</span>: <span class="hljs-title class_">String</span> <span class="hljs-title class_">Captain</span> <span class="hljs-title class_">Jack</span> <span class="hljs-title class_">Sparrow</span>
</pre><p><br></p>](
/uploads/brochures/post_sidebar/8qnusvf58eltoxk65vxy-61968b399f1c5.jpg?v=2.2)
![<p>Короткая история как получить доступ к переменной php, если ее зона видимости ограничена без ReflectionMethod<span style="color: rgb(230, 0, 0);">*</span> магии.</p><blockquote><strong>public</strong> - Class members declared public can be accessed everywhere.</blockquote><blockquote><strong>protected</strong> - Class members declared protected can be accessed only within the class itself and by inheriting and parent classes.</blockquote><blockquote><strong>private</strong> - Class members declared as private may only be accessed by the class that defines the member.</blockquote><p><strong><u>Важно</u></strong>, объекты одного типа будут иметь доступ к свойствам друг друга вне зависимости от их зоны видимости даже если они инициализированы в разных местах</p><p>Создадим класс с private свойством и получим доступ к нему:</p><pre class="ql-syntax" spellcheck="false"><span class="hljs-meta"><?php</span>
<span class="hljs-class"><span class="hljs-keyword">class</span> <span class="hljs-title">Test</span>
</span>{
<span class="hljs-keyword">private</span> <span class="hljs-variable">$secret</span>;
<span class="hljs-keyword">public</span> <span class="hljs-function"><span class="hljs-keyword">function</span> <span class="hljs-title">__construct</span>(<span class="hljs-params"><span class="hljs-keyword">string</span> <span class="hljs-variable">$secret</span></span>)
</span>{
<span class="hljs-keyword">$this</span>->secret = <span class="hljs-variable">$secret</span>;
}
<span class="hljs-keyword">public</span> <span class="hljs-function"><span class="hljs-keyword">function</span> <span class="hljs-title">access</span>(<span class="hljs-params">Test <span class="hljs-variable">$other</span></span>)
</span>{
var_dump(<span class="hljs-string">'access to private'</span>);
var_dump(<span class="hljs-variable">$other</span>->secret);
}
}
<span class="hljs-variable">$r</span> = <span class="hljs-keyword">new</span> Test(<span class="hljs-string">'init class'</span>);
<span class="hljs-variable">$r</span>->access(<span class="hljs-keyword">new</span> Test(<span class="hljs-string">'Luke, I am your father.'</span>));
<span class="hljs-comment">//expected output</span>
<span class="hljs-comment">//access</span>
<span class="hljs-comment">//Luke, I am your father.</span>
</pre><p>Как мы можем это использовать, например, поменять значение с переменной без сеттера и даже можем инициализировать класс с приватным конструктором</p><pre class="ql-syntax" spellcheck="false"><span class="hljs-meta"><?php</span>
<span class="hljs-class"><span class="hljs-keyword">class</span> <span class="hljs-title">Test</span> </span>{
<span class="hljs-keyword">private</span> <span class="hljs-keyword">string</span> <span class="hljs-variable">$name</span>;
<span class="hljs-keyword">private</span> <span class="hljs-function"><span class="hljs-keyword">function</span> <span class="hljs-title">__construct</span>() </span>{}
<span class="hljs-keyword">public</span> <span class="hljs-function"><span class="hljs-keyword">function</span> <span class="hljs-title">getName</span>(): <span class="hljs-title">string</span> </span>{
<span class="hljs-keyword">return</span> <span class="hljs-keyword">$this</span>->name;
}
<span class="hljs-keyword">public</span> <span class="hljs-built_in">static</span> <span class="hljs-function"><span class="hljs-keyword">function</span> <span class="hljs-title">setFromConfig</span>(<span class="hljs-params"><span class="hljs-keyword">array</span> <span class="hljs-variable">$row</span></span>): <span class="hljs-title">self</span> </span>{
<span class="hljs-variable">$Test</span> = <span class="hljs-keyword">new</span> Test;
<span class="hljs-variable">$Test</span>->name = <span class="hljs-variable">$row</span>[<span class="hljs-string">'name'</span>];
<span class="hljs-keyword">return</span> <span class="hljs-variable">$Test</span>;
}
}
<span class="hljs-variable">$Test</span> = Test::setFromConfig([<span class="hljs-string">'name'</span>=><span class="hljs-string">'Harry Potter'</span>]);
<span class="hljs-keyword">echo</span> <span class="hljs-variable">$Test</span>->getName();
</pre><p><br></p><p><strong>PS</strong></p><p><span style="color: rgb(230, 0, 0);">*</span>Как получить доступ к private переменной используя reflection</p><pre class="ql-syntax" spellcheck="false"><span class="hljs-meta"><?php</span>
<span class="hljs-class"><span class="hljs-keyword">class</span> <span class="hljs-title">Foo</span>
</span>{
<span class="hljs-keyword">private</span> <span class="hljs-variable">$privateProperty</span> = <span class="hljs-string">'Harry Potter!'</span>;
}
<span class="hljs-variable">$method</span> = <span class="hljs-keyword">new</span> ReflectionProperty(<span class="hljs-string">'Foo'</span>, <span class="hljs-string">'privateProperty'</span>);
<span class="hljs-variable">$method</span>->setAccessible(<span class="hljs-literal">true</span>);
<span class="hljs-keyword">echo</span> <span class="hljs-variable">$method</span>->getValue(<span class="hljs-keyword">new</span> Foo);
<span class="hljs-comment">// Expected output</span>
<span class="hljs-comment">// Harry Potter!</span>
</pre>](
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