---
title: Number 和 String 函數
slug: conflicting/Web/JavaScript/Guide/Functions_536f6bf46bbdf38cc1a0b28ca1bc41b9
translation_of: Web/JavaScript/Guide/Functions
translation_of_original: >-
  Web/JavaScript/Guide/Obsolete_Pages/Predefined_Functions/parseInt_and_parseFloat_Functions
original_slug: >-
  Web/JavaScript/Obsolete_Pages/Obsolete_Pages/Obsolete_Pages/預先定義的函數/Number_和_String_函數
---
<h4 id="Number_和_String_函數">Number 和 String 函數</h4>
<div class="onlyinclude">
<p><code>Number</code> 和 <code>String</code> 函數讓你把物件轉換為數字或字串。這些函數的語句是︰</p>
<pre>var objRef=Number(objRef);
var objRef=String(objRef);
</pre>
<p>此處的 <code>objRef</code> 就是物件的參考。</p>
<p>以下的範例把 <code><a class="internal" href="/zh_tw/Core_JavaScript_1.5_%E5%8F%83%E8%80%83/%E5%85%A8%E5%9F%9F%E7%89%A9%E4%BB%B6/Date" title="zh tw/Core JavaScript 1.5 參考/全域物件/Date">Date</a></code> 物件轉換為可讀的字串。</p>
<pre>var D = new Date (430054663215);
// 返回以下字串
// "Thu Aug 18 04:37:43 GMT-0700 (Pacific Daylight Time) 1983"
var x = String(D);
</pre>
</div>
<p> </p>
<p>以下範例把 <code><a class="internal" href="/zh_tw/Core_JavaScript_1.5_%E5%8F%83%E8%80%83/%E5%85%A8%E5%9F%9F%E7%89%A9%E4%BB%B6/String" title="zh tw/Core JavaScript 1.5 參考/全域物件/String">String</a></code> 物件轉換為 <a class="internal" href="/zh_tw/Core_JavaScript_1.5_%E5%8F%83%E8%80%83/%E5%85%A8%E5%9F%9F%E7%89%A9%E4%BB%B6/Number" title="zh tw/Core JavaScript 1.5 參考/全域物件/Number"><font face="Courier New">Number</font></a> 物件。</p>
<pre>var str="12";
var num=Number(str);
</pre>
<p>你可以使用 DOM 的方法 write() 和 JavaScript 的 typeof 運算子來檢驗。</p>
<pre>var str="12";
document.write(typeof str);
document.write("&lt;br/&gt;");
var num=Number(str);
document.write(typeof num);
</pre>
<p> {{ PreviousNext("Core_JavaScript_1.5_教學:預先定義的函數:parseInt_和_parseFloat_函數", "Core_JavaScript_1.5_教學:預先定義的函數:escape_和_unescape_函數") }}</p>
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