点击运行
<!DOCTYPE html> <html> <body> <h2>JavaScript 数据类型</h2> <p>Undefined and null are equal in value but different in type:</p> <p id="demo"></p> <script> document.getElementById("demo").innerHTML = typeof undefined + "<br>" + typeof null + "<br><br>" + (null === undefined) + "<br>" + (null == undefined); </script> </body> </html>
运行结果
