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author | Peter Bengtsson <mail@peterbe.com> | 2020-12-08 14:42:17 -0500 |
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committer | Peter Bengtsson <mail@peterbe.com> | 2020-12-08 14:42:17 -0500 |
commit | da78a9e329e272dedb2400b79a3bdeebff387d47 (patch) | |
tree | e6ef8aa7c43556f55ddfe031a01cf0a8fa271bfe /files/it/web/javascript/reference/global_objects/math/floor | |
parent | 1109132f09d75da9a28b649c7677bb6ce07c40c0 (diff) | |
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diff --git a/files/it/web/javascript/reference/global_objects/math/floor/index.html b/files/it/web/javascript/reference/global_objects/math/floor/index.html new file mode 100644 index 0000000000..3f7f6c7851 --- /dev/null +++ b/files/it/web/javascript/reference/global_objects/math/floor/index.html @@ -0,0 +1,158 @@ +--- +title: Math.floor() +slug: Web/JavaScript/Reference/Global_Objects/Math/floor +translation_of: Web/JavaScript/Reference/Global_Objects/Math/floor +--- +<div>{{JSRef}}</div> + +<p>La funzione <strong><code>Math.floor()</code></strong> restituisce il numero intero, arrotondato per difetto, del numero passato come parametro.</p> + +<h2 id="Sintassi">Sintassi</h2> + +<pre class="syntaxbox"><code>Math.floor(<var>x</var>)</code></pre> + +<h3 id="Parametri">Parametri</h3> + +<dl> + <dt><code>x</code></dt> + <dd>Un numero.</dd> +</dl> + +<h3 id="Valore_di_ritorno">Valore di ritorno</h3> + +<p>Un numero intero rappresentante l'arrotondamento per difetto del numero passato come parametro.</p> + +<h2 id="Descrizione">Descrizione</h2> + +<p>Siccome <code>floor()</code> è un metodo statico di <code>Math</code>, viene sempre usato come <code>Math.floor()</code> piuttosto che come metodo di un oggetto <code>Math</code> creato in precedenza (<code>Math</code> non è un costruttore).</p> + +<h2 id="Esempi">Esempi</h2> + +<h3 id="Math.floor()"><code>Math.floor()</code></h3> + +<pre class="brush: js">Math.floor( 45.95); // 45 +Math.floor( 45.05); // 45 +Math.floor( 4 ); // 4 +Math.floor(-45.05); // -46 +Math.floor(-45.95); // -46 +</pre> + +<h3 id="Arrotondamento_decimale">Arrotondamento decimale</h3> + +<pre class="brush: js">// Closure +(function() { + /** + * Decimal adjustment of a number. + * + * @param {String} type The type of adjustment. + * @param {Number} value The number. + * @param {Integer} exp The exponent (the 10 logarithm of the adjustment base). + * @returns {Number} The adjusted value. + */ + function decimalAdjust(type, value, exp) { + // If the exp is undefined or zero... + if (typeof exp === 'undefined' || +exp === 0) { + return Math[type](value); + } + value = +value; + exp = +exp; + // If the value is not a number or the exp is not an integer... + if (isNaN(value) || !(typeof exp === 'number' && exp % 1 === 0)) { + return NaN; + } + // Shift + value = value.toString().split('e'); + value = Math[type](+(value[0] + 'e' + (value[1] ? (+value[1] - exp) : -exp))); + // Shift back + value = value.toString().split('e'); + return +(value[0] + 'e' + (value[1] ? (+value[1] + exp) : exp)); + } + + // Decimal round + if (!Math.round10) { + Math.round10 = function(value, exp) { + return decimalAdjust('round', value, exp); + }; + } + // Decimal floor + if (!Math.floor10) { + Math.floor10 = function(value, exp) { + return decimalAdjust('floor', value, exp); + }; + } + // Decimal ceil + if (!Math.ceil10) { + Math.ceil10 = function(value, exp) { + return decimalAdjust('ceil', value, exp); + }; + } +})(); + +// Round +Math.round10(55.55, -1); // 55.6 +Math.round10(55.549, -1); // 55.5 +Math.round10(55, 1); // 60 +Math.round10(54.9, 1); // 50 +Math.round10(-55.55, -1); // -55.5 +Math.round10(-55.551, -1); // -55.6 +Math.round10(-55, 1); // -50 +Math.round10(-55.1, 1); // -60 +// Floor +Math.floor10(55.59, -1); // 55.5 +Math.floor10(59, 1); // 50 +Math.floor10(-55.51, -1); // -55.6 +Math.floor10(-51, 1); // -60 +// Ceil +Math.ceil10(55.51, -1); // 55.6 +Math.ceil10(51, 1); // 60 +Math.ceil10(-55.59, -1); // -55.5 +Math.ceil10(-59, 1); // -50 +</pre> + +<h2 id="Specifiche">Specifiche</h2> + +<table class="standard-table"> + <tbody> + <tr> + <th scope="col">Specifica</th> + <th scope="col">Stato</th> + <th scope="col">Commento</th> + </tr> + <tr> + <td>{{SpecName('ES1')}}</td> + <td>{{Spec2('ES1')}}</td> + <td>Definizione iniziale. Implementata in JavaScript 1.0.</td> + </tr> + <tr> + <td>{{SpecName('ES5.1', '#sec-15.8.2.9', 'Math.floor')}}</td> + <td>{{Spec2('ES5.1')}}</td> + <td> </td> + </tr> + <tr> + <td>{{SpecName('ES6', '#sec-math.floor', 'Math.floor')}}</td> + <td>{{Spec2('ES6')}}</td> + <td> </td> + </tr> + <tr> + <td>{{SpecName('ESDraft', '#sec-math.floor', 'Math.floor')}}</td> + <td>{{Spec2('ESDraft')}}</td> + <td> </td> + </tr> + </tbody> +</table> + +<h2 id="Compatibilità_dei_Browser">Compatibilità dei Browser</h2> + +<p class="hidden">The compatibility table in this page is generated from structured data. If you'd like to contribute to the data, please check out <a href="https://github.com/mdn/browser-compat-data">https://github.com/mdn/browser-compat-data</a> and send us a pull request.</p> + +<p>{{Compat("javascript.builtins.Math.floor")}}</p> + +<h2 id="Vedi_anche">Vedi anche</h2> + +<ul> + <li>{{jsxref("Math.abs()")}}</li> + <li>{{jsxref("Math.ceil()")}}</li> + <li>{{jsxref("Math.round()")}}</li> + <li>{{jsxref("Math.sign()")}}</li> + <li>{{jsxref("Math.trunc()")}}</li> +</ul> |