点击运行
<!DOCTYPE html> <html> <body> <h2>JavaScript 数据类型</h2> <p>无值变量的值和数据类型是 <b>undefined</b>。</p> <p id="demo"></p> <script> var car; document.getElementById("demo").innerHTML = car + "<br>" + typeof car; </script> </body> </html>
运行结果
