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diff --git a/files/he/web/javascript/reference/statements/for...of/index.html b/files/he/web/javascript/reference/statements/for...of/index.html new file mode 100644 index 0000000000..86edb2f69e --- /dev/null +++ b/files/he/web/javascript/reference/statements/for...of/index.html @@ -0,0 +1,269 @@ +--- +title: for...of +slug: Web/JavaScript/Reference/Statements/for...of +translation_of: Web/JavaScript/Reference/Statements/for...of +--- +<div>{{jsSidebar("Statements")}}</div> + +<div> </div> + +<div>הצהרת <strong><code>for...of </code></strong>יוצרת לולאה ע"ג<code> </code><a href="/en-US/docs/Web/JavaScript/Reference/Iteration_protocols#iterable">iterable objects</a> (שכולל {{jsxref("Array")}}, {{jsxref("Map")}}, {{jsxref("Set")}}, {{jsxref("String")}}, {{jsxref("TypedArray")}}, <a href="/en-US/docs/Web/JavaScript/Reference/Functions_and_function_scope/arguments">arguments</a> object וכן הלאה..),</div> + +<div>invoking a custom iteration hook with statements to be executed for the value of each distinct property.</div> + +<h2 id="Syntax">Syntax</h2> + +<pre class="syntaxbox">for (<em>variable</em> of <em>iterable</em>) { + <em>statement +</em>} +</pre> + +<dl> + <dt><code>variable</code></dt> + <dd>בכל איטרציה, ערך ה property הנוכחי של <em>iterable </em>מוקצה ל <em>variable</em></dd> + <dt>iterable</dt> + <dd>אובייקט עם properties ברי איטרציה</dd> +</dl> + +<h3 id="לדוגמא"><span style="font-size: 14px; letter-spacing: normal;">לדוגמא:</span></h3> + +<h3 id="איטרציה_עג_jsxref(Array)">איטרציה ע"ג {{jsxref("Array")}}</h3> + +<pre class="brush:js">let iterable = [10, 20, 30]; + +for (let value of iterable) { + console.log(value); +} +// 10 +// 20 +// 30 +</pre> + +<p>אפשר להשתמש ג"כ ב <code><a href="/en-US/docs/Web/JavaScript/Reference/Statements/const">const</a> </code>במקום <code><a href="/en-US/docs/Web/JavaScript/Reference/Statements/let">let</a> </code>באם אתה לא משנה את ערך המשתנה בתוך הבלוק.</p> + +<p> </p> + +<p>איטרציה ע"ג {{jsxref("String")}}</p> + +<pre class="brush:js">let iterable = "boo"; + +for (let value of iterable) { + console.log(value); +} +// "b" +// "o" +// "o" +</pre> + +<h3 id="Iterating_over_a_jsxref(TypedArray)">Iterating over a {{jsxref("TypedArray")}}</h3> + +<pre class="brush:js">let iterable = new Uint8Array([0x00, 0xff]); + +for (let value of iterable) { + console.log(value); +} +// 0 +// 255 +</pre> + +<h3 id="Iterating_over_a_jsxref(Map)">Iterating over a {{jsxref("Map")}}</h3> + +<pre class="brush:js">let iterable = new Map([["a", 1], ["b", 2], ["c", 3]]); + +for (let entry of iterable) { + console.log(entry); +} +// [a, 1] +// [b, 2] +// [c, 3] + +for (let [key, value] of iterable) { + console.log(value); +} +// 1 +// 2 +// 3 +</pre> + +<h3 id="Iterating_over_a_jsxref(Set)">Iterating over a {{jsxref("Set")}}</h3> + +<pre class="brush:js">let iterable = new Set([1, 1, 2, 2, 3, 3]); + +for (let value of iterable) { + console.log(value); +} +// 1 +// 2 +// 3 +</pre> + +<h3 id="Iterating_over_a_DOM_collection">Iterating over a DOM collection</h3> + +<p>Iterating over DOM collections like {{domxref("NodeList")}}: the following example adds a <code>read</code> class to paragraphs that are direct descendants of an article:</p> + +<pre class="brush:js">// Note: This will only work in platforms that have +// implemented NodeList.prototype[Symbol.iterator] +let articleParagraphs = document.querySelectorAll("article > p"); + +for (let paragraph of articleParagraphs) { + paragraph.classList.add("read"); +} +</pre> + +<h3 id="Iterating_over_generators">Iterating over generators</h3> + +<p>You can also iterate over <a href="/en-US/docs/Web/JavaScript/Reference/Statements/function*">generators</a>:</p> + +<pre class="brush:js">function* fibonacci() { // a generator function + let [prev, curr] = [1, 1]; + while (true) { + [prev, curr] = [curr, prev + curr]; + yield curr; + } +} + +for (let n of fibonacci()) { + console.log(n); + // truncate the sequence at 1000 + if (n >= 1000) { + break; + } +} +</pre> + +<h3 id="Iterating_over_other_iterable_objects">Iterating over other iterable objects</h3> + +<p>You can also iterate over an object that explicitly implements <a href="/en-US/docs/Web/JavaScript/Reference/Iteration_protocols#iterable">iterable</a> protocol:</p> + +<pre class="brush:js">var iterable = { + [Symbol.iterator]() { + return { + i: 0, + next() { + if (this.i < 3) { + return { value: this.i++, done: false }; + } + return { value: undefined, done: true }; + } + }; + } +}; + +for (var value of iterable) { + console.log(value); +} +// 0 +// 1 +// 2 +</pre> + +<h3 id="Difference_between_for...of_and_for...in">Difference between <code>for...of</code> and <code>for...in</code></h3> + +<p>The <code><a href="/en-US/docs/Web/JavaScript/Reference/Statements/for...in">for...in</a></code> loop will iterate over all enumerable properties of an object.</p> + +<p>The <code>for...of</code> syntax is specific to <strong>collections</strong>, rather than all objects. It will iterate in this manner over the elements of any collection that has a <code>[Symbol.iterator]</code> property.</p> + +<p>The following example shows the difference between a <code>for...of</code> loop and a <code>for...in</code> loop.</p> + +<pre class="brush:js">Object.prototype.objCustom = function () {}; +Array.prototype.arrCustom = function () {}; + +let iterable = [3, 5, 7]; +iterable.foo = "hello"; + +for (let i in iterable) { + console.log(i); // logs 0, 1, 2, "foo", "arrCustom", "objCustom" +} + +for (let i of iterable) { + console.log(i); // logs 3, 5, 7 +} +</pre> + +<h2 id="Specifications">Specifications</h2> + +<table class="standard-table"> + <tbody> + <tr> + <th scope="col">Specification</th> + <th scope="col">Status</th> + <th scope="col">Comment</th> + </tr> + <tr> + <td>{{SpecName('ES6', '#sec-for-in-and-for-of-statements', 'for...of statement')}}</td> + <td>{{Spec2('ES6')}}</td> + <td>Initial definition.</td> + </tr> + <tr> + <td>{{SpecName('ESDraft', '#sec-for-in-and-for-of-statements', 'for...of statement')}}</td> + <td>{{Spec2('ESDraft')}}</td> + <td> </td> + </tr> + </tbody> +</table> + +<h2 id="Browser_compatibility">Browser compatibility</h2> + +<p>{{CompatibilityTable}}</p> + +<div id="compat-desktop"> +<table class="compat-table"> + <tbody> + <tr> + <th>Feature</th> + <th>Chrome</th> + <th>Firefox (Gecko)</th> + <th>Edge</th> + <th>Opera</th> + <th>Safari</th> + </tr> + <tr> + <td>Basic support</td> + <td>{{CompatChrome(38)}} <a href="#Chrome_note_1">[1]</a><br> + {{CompatChrome(51)}} <a href="#Chrome_note_3">[3]</a></td> + <td>{{CompatGeckoDesktop("13")}} <a href="#Gecko_note_2">[2]</a></td> + <td>12</td> + <td>25</td> + <td>7.1</td> + </tr> + </tbody> +</table> +</div> + +<div id="compat-mobile"> +<table class="compat-table"> + <tbody> + <tr> + <th>Feature</th> + <th>Android</th> + <th>Chrome for Android</th> + <th>Firefox Mobile (Gecko)</th> + <th>IE Mobile</th> + <th>Opera Mobile</th> + <th>Safari Mobile</th> + </tr> + <tr> + <td>Basic support</td> + <td>5.1</td> + <td>{{CompatChrome(38)}} [1]</td> + <td>{{CompatGeckoMobile("13")}} [2]</td> + <td>{{CompatNo}}</td> + <td>{{CompatUnknown}}</td> + <td>8</td> + </tr> + </tbody> +</table> +</div> + +<p><a name="Chrome_note_1">[1]</a> From Chrome 29 to Chrome 37 this feature was available behind a preference. In chrome://flags/#enable-javascript-harmony, activate the entry “Enable Experimental JavaScript”.</p> + +<p><a name="Gecko_note_2">[2]</a> Prior Firefox 51, using the <code>for...of</code> loop construct with the <code><a href="/en-US/docs/Web/JavaScript/Reference/Statements/const">const</a></code> keyword threw a {{jsxref("SyntaxError")}} ("missing = in const declaration"). This has been fixed ({{bug(1101653)}}).</p> + +<p><a name="Chrome_note_3">[3]</a> Support for iteration of objects was added in Chrome 51.</p> + +<h2 id="See_also">See also</h2> + +<ul> + <li>{{jsxref("Array.prototype.forEach()")}}</li> + <li><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/Map/forEach">Map.prototype.forEach()</a></li> +</ul> |