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authorPeter Bengtsson <mail@peterbe.com>2020-12-08 14:42:17 -0500
committerPeter Bengtsson <mail@peterbe.com>2020-12-08 14:42:17 -0500
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+---
+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' &amp;&amp; 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>