Click events are added to login, but the page will be refreshed when jumping, but it is possible to click Enter.

• Among them, the landing tag reads like this

<a class="lgBut" id="btn_login" href="" >Sign in</a>

• This is the way below.

   $("btn_login").click(function(){
	    var USERNAME=$("#USERNAME").val();
	    var PASSWORD=$("#PASSWORD").val();
	    $.ajax({
	        type:'get',
	        url:  address + "/appchange/appLogin?"+Math.random(),
	        data: {
	            USERNAME: USERNAME, PASSWORD: PASSWORD
	        },
	        xhrFields: {
	            withCredentials: true
	        },
	        crossDomain: true,
	        cache:false,
	        dataType:'json',
	        success:function(data){
	            if (data.info == "success") {
	                window.localStorage.errortimes=0;
	                window.localStorage.userinfo=JSON.stringify(data.USER);
	                window.localStorage.USER_CODE=data.USER.USER_CODE;      					if(window.localStorage.href==undefined||window.localStorage.href=="")
	                {
	                    window.location.href="index.html";
	                }
	                else{
	                    window.location.href=window.localStorage.href;
	                    window.localStorage.href="";
	                }
	                window.localStorage.logintime=new Date();
	            }
	            else{
	            	 layer.msg(data.info);
	                window.localStorage.errortimes++;
	            }
	        },
	        error:function(ex){
				
	        }
	    });
	});
	$(document).keyup(function(event){
        if(event.keyCode ==13){
           login();
        }
    });

Later, it was found that the href in the login tag played a role, and that the $("btn_login").click(function(){} event would execute everything in the a tag, while when returning, only one click {} method was executed. If href = ", the href was executed when ajax was executed, and the page was refreshed before ajax was executed, so the page would be refreshed.