---
title: 預先定義的函數
slug: conflicting/Web/JavaScript/Guide/Functions_587eb671a310bac0771e73a91b0abe6d
translation_of: Web/JavaScript/Guide/Functions
translation_of_original: Web/JavaScript/Guide/Obsolete_Pages/Predefined_Functions
original_slug: Web/JavaScript/Obsolete_Pages/Obsolete_Pages/Obsolete_Pages/預先定義的函數
---
<p> </p>
<div class="onlyinclude">
<h3 id="預先定義的函數" name="預先定義的函數">預先定義的函數</h3>
<p>JavaScript 有一些最頂層的已預先定義的函數︰</p>
<ul> <li><a href="/zh%20tw/Core_JavaScript_1.5_%E6%95%99%E5%AD%B8/%E9%A0%90%E5%85%88%E5%AE%9A%E7%BE%A9%E7%9A%84%E5%87%BD%E6%95%B8/eval_%E5%87%BD%E6%95%B8" title="zh tw/Core_JavaScript_1.5_教學/預先定義的函數/eval_函數">eval</a></li> <li><a href="/zh%20tw/Core_JavaScript_1.5_%E6%95%99%E5%AD%B8/%E9%A0%90%E5%85%88%E5%AE%9A%E7%BE%A9%E7%9A%84%E5%87%BD%E6%95%B8/isFinite_%E5%87%BD%E6%95%B8" title="zh tw/Core_JavaScript_1.5_教學/預先定義的函數/isFinite_函數">isFinite</a></li> <li><a href="/zh%20tw/Core_JavaScript_1.5_%E6%95%99%E5%AD%B8/%E9%A0%90%E5%85%88%E5%AE%9A%E7%BE%A9%E7%9A%84%E5%87%BD%E6%95%B8/isNaN_%E5%87%BD%E6%95%B8" title="zh tw/Core_JavaScript_1.5_教學/預先定義的函數/isNaN_函數">isNaN</a></li> <li><a href="/zh%20tw/Core_JavaScript_1.5_%E6%95%99%E5%AD%B8/%E9%A0%90%E5%85%88%E5%AE%9A%E7%BE%A9%E7%9A%84%E5%87%BD%E6%95%B8/parseInt_%E5%92%8C_parseFloat_%E5%87%BD%E6%95%B8" title="zh tw/Core_JavaScript_1.5_教學/預先定義的函數/parseInt_和_parseFloat_函數">parseInt 和 parseFloat</a></li> <li><a href="/zh%20tw/Core_JavaScript_1.5_%E6%95%99%E5%AD%B8/%E9%A0%90%E5%85%88%E5%AE%9A%E7%BE%A9%E7%9A%84%E5%87%BD%E6%95%B8/Number_%E5%92%8C_String_%E5%87%BD%E6%95%B8" title="zh tw/Core_JavaScript_1.5_教學/預先定義的函數/Number_和_String_函數">Number 和 String</a></li> <li><a href="/zh%20tw/Core_JavaScript_1.5_%E6%95%99%E5%AD%B8/%E9%A0%90%E5%85%88%E5%AE%9A%E7%BE%A9%E7%9A%84%E5%87%BD%E6%95%B8/escape_%E5%92%8C_unescape_%E5%87%BD%E6%95%B8" title="zh tw/Core_JavaScript_1.5_教學/預先定義的函數/escape_和_unescape_函數">encodeURI、decodeURI、encodeURIComponent、decodeURIComponent（Javascript 1.5 以後的版本皆可使用）。</a></li>
</ul>
</div>
<p>{{ PreviousNext("Core_JavaScript_1.5_教學:arguments_物件的使用", "Core_JavaScript_1.5_教學:預先定義的函數:eval_函數") }}</p>
<p>{{ languages( { "en": "en/Core_JavaScript_1.5_Guide/Predefined_Functions", "fr": "fr/Guide_JavaScript_1.5/Fonctions_pr\u00e9d\u00e9finies", "ja": "ja/Core_JavaScript_1.5_Guide/Predefined_Functions", "pl": "pl/Przewodnik_po_j\u0119zyku_JavaScript_1.5/Funkcje_predefiniowane" } ) }}</p>