<!DOCTYPE html> <html> <body> <h1>JavaScript String 方法</h1> <p>如果未找到文本,indexOf() 和 lastIndexOf() 都返回 -1:</p> <p id="demo"></p> <script> let str = "Please locate where 'locate' occurs!"; document.getElementById("demo").innerHTML = str.indexOf("Bill"); </script> </body> </html>