//The picture is displayed centered in the div:
//javascript removes spaces at both ends
var pwd=" 123 ";
pwd=pwd.replace(/^s+|s+$/g, "" );//pwd="123"
//javascript scrolls back to the top of the interface
window.scrollTo(0,0);
//javascript regular expression to determine whether the string is composed entirely of numeric characters
if( str.match(/d/)== null)
alert("The value entered is wrong!");
else
alert("The value is correct!");
![[Web front-end] Node.js quick start](https://img.php.cn/upload/course/000/000/067/662b5d34ba7c0227.png)
