# indexof() indexOf() 方法可返回某個指定的字符串值在字符串中首次出現的位置。 ## 提示和注釋 注釋：indexOf() 方法對大小寫敏感！ 注釋：如果要檢索的字符串值沒有出現，則該方法返回 -1 ## 實例 在本例中，我們將在 "Hello world!" 字符串內進行不同的檢索： ``` <pre class="calibre13">``` <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">indexOf</span><span class="token1">(</span><span class="token4">"Hello"</span><span class="token1">)</span> <span class="token">+</span> <span class="token4">"<br />"</span><span class="token1">)</span> document<span class="token1">.</span><span class="token3">write</span><span class="token1">(</span>str<span class="token1">.</span><span class="token3">indexOf</span><span class="token1">(</span><span class="token4">"World"</span><span class="token1">)</span> <span class="token">+</span> <span class="token4">"<br />"</span><span class="token1">)</span> document<span class="token1">.</span><span class="token3">write</span><span class="token1">(</span>str<span class="token1">.</span><span class="token3">indexOf</span><span class="token1">(</span><span class="token4">"world"</span><span class="token1">)</span><span class="token1">)</span> <span class="token"><</span><span class="token">/</span>script<span class="token">></span> ``` ``` 以上代碼的輸出： ``` <pre class="calibre14">``` <span class="token5">0</span> <span class="token">-</span><span class="token5">1</span> <span class="token5">6</span> ``` ```