# toLowerCase()基本使用 ## 定義和用法 toLowerCase() 方法用于把字符串轉換為小寫。 ``` <pre class="calibre13">``` stringObject<span class="token1">.</span><span class="token3">toLowerCase</span><span class="token1">(</span><span class="token1">)</span> ``` ``` 一個新的字符串，在其中 stringObject 的所有大寫字符全部被轉換為了小寫字符。 ## 實例 在本例中，"Hello world!" 將以小寫字母來顯示： ``` <pre class="calibre14">``` <span class="token"><</span>script type<span class="token">=</span><span class="token4">"text/javascript"</span><span class="token">></span> <span class="token2">var</span> str<span class="token">=</span><span class="token4">"Hello World!"</span> document<span class="token1">.</span><span class="token3">write</span><span class="token1">(</span>str<span class="token1">.</span><span class="token3">toLowerCase</span><span class="token1">(</span><span class="token1">)</span><span class="token1">)</span> <span class="token"><</span><span class="token">/</span>script<span class="token">></span> ``` ```