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| author | Peter Bengtsson <mail@peterbe.com> | 2020-12-08 14:41:45 -0500 |
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| committer | Peter Bengtsson <mail@peterbe.com> | 2020-12-08 14:41:45 -0500 |
| commit | 1109132f09d75da9a28b649c7677bb6ce07c40c0 (patch) | |
| tree | 0dd8b084480983cf9f9680e8aedb92782a921b13 /files/fa/web/javascript/reference/errors/too_much_recursion | |
| parent | 4b1a9203c547c019fc5398082ae19a3f3d4c3efe (diff) | |
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diff --git a/files/fa/web/javascript/reference/errors/too_much_recursion/index.html b/files/fa/web/javascript/reference/errors/too_much_recursion/index.html new file mode 100644 index 0000000000..02a8d54c45 --- /dev/null +++ b/files/fa/web/javascript/reference/errors/too_much_recursion/index.html @@ -0,0 +1,114 @@ +--- +title: 'InternalError: too much recursion' +slug: Web/JavaScript/Reference/Errors/Too_much_recursion +translation_of: Web/JavaScript/Reference/Errors/Too_much_recursion +--- +<div>{{jsSidebar("Errors")}}</div> + +<h2 id="Message">Message</h2> + +<pre class="syntaxbox">Error: Out of stack space (Edge) +InternalError: too much recursion (Firefox) +RangeError: Maximum call stack size exceeded (Chrome) +</pre> + +<h2 id="Error_type">Error type</h2> + +<p>{{jsxref("InternalError")}}.</p> + +<h2 id="What_went_wrong">What went wrong?</h2> + +<p>A function that calls itself is called a <em>recursive function</em>. Once a condition is met, the function stops calling itself. This is called a <em>base case</em>.</p> + +<p>In some ways, recursion is analogous to a loop. Both execute the same code multiple times, and both require a condition (to avoid an infinite loop, or rather, infinite recursion in this case). <span class="seoSummary">When there are too many function calls, or a function is missing a base case, JavaScript will throw this error.</span></p> + +<h2 id="Examples">Examples</h2> + +<p>This recursive function runs 10 times, as per the exit condition.</p> + +<pre class="brush: js">function loop(x) { + if (x >= 10) // "x >= 10" is the exit condition + return; + // do stuff + loop(x + 1); // the recursive call +} +loop(0);</pre> + +<p>Setting this condition to an extremely high value, won't work:</p> + +<pre class="brush: js example-bad">function loop(x) { + if (x >= 1000000000000) + return; + // do stuff + loop(x + 1); +} +loop(0); + +// InternalError: too much recursion</pre> + +<p>This recursive function is missing a base case. As there is no exit condition, the function will call itself infinitely.</p> + +<pre class="brush: js example-bad">function loop(x) { + // The base case is missing + +loop(x + 1); // Recursive call +} + +loop(0); + +// InternalError: too much recursion</pre> + +<h3 id="Class_error_too_much_recursion">Class error: too much recursion</h3> + +<pre class="brush: js example-bad">class Person{ + constructor(){} + set name(name){ + this.name = name; // Recursive call + } +} + + +const tony = new Person(); +tony.name = "Tonisha"; // InternalError: too much recursion +</pre> + +<p>When a value is assigned to the property name (this.name = name;) JavaScript needs to set that property. When this happens, the setter function is triggered.</p> + +<pre class="brush: js example-bad">set name(name){ + this.name = name; // Recursive call +} +</pre> + +<div class="note"> +<p>In this example when the setter is triggered, it is told to do the same thing again: <em>to set the same property that it is meant to handle.</em> This causes the function to call itself, again and again, making it infinitely recursive.</p> +</div> + +<p>This issue also appears if the same variable is used in the getter.</p> + +<pre class="brush: js example-bad">get name(){ + return this.name; // Recursive call +} +</pre> + +<p>To avoid this problem, make sure that the property being assigned to inside the setter function is different from the one that initially triggered the setter.The same goes for the getter.</p> + +<pre class="brush: js">class Person{ + constructor(){} + set name(name){ + this._name = name; + } + get name(){ + return this._name; + } +} +const tony = new Person(); +tony.name = "Tonisha"; +console.log(tony); +</pre> + +<h2 id="See_also">See also</h2> + +<ul> + <li>{{Glossary("Recursion")}}</li> + <li><a href="/en-US/docs/Web/JavaScript/Guide/Functions#Recursion">Recursive functions</a></li> +</ul> |
