EJS in HTML not working - html

Question

is this a correct syntax for EJS technology in HTML ? The "flash object" is send from controller . Here it is my "log in" action in Controller and HTML code. I want a peace of HTML is executed base on the content of "flash object". But it doesn't work.This is controller in back end:
login: function(req, res){
var x = new LdapService();
x.login(req.body.userid, req.body.password, function(isAuth){
if(isAuth ){
res.send('successful login');
}
else{
res.view('login/index', {locals: {flash: req.flash('error', 'Wrong Credentials')}}) ;
}
});
},
=============================================
Here it is the HTML code in front end.
<% if (req.flash('error')!=''){ %>
<p>Hi</p>
<p><%- (req.flash('error')) %></p>
<div class="box-body">
<div class="alert alert-danger alert-dismissable">
<i class="fa fa-ban"></i>
<button type="button" class="close" data-dismiss="alert" aria-hidden="true">×</button>
<b>Alert!</b> Wrong
</div>
</div>
<% } %>

Answer 1

Once you access the flash object using req.flash, its value is cleared. So the conditional test will clear the flash object.
The value is also stored in the session, so I test the session directly before displaying the flash value.
<% if(req.session.flash && req.session.flash.error){ %>
<div class="row form-row m-l-20 m-r-20 xs-m-l-10 xs-m-r-10">
<div class="alert alert-error">
<button class="close" data-dismiss="alert"></button>
<%- req.flash('error') %>
</div>
</div>
<% }%>

Answer 2

It's not entirely clear why you need to use flash messages in this case, since you're setting the message and displaying it in the same request. Flash messages are more appropriate when you're setting a message and then redirecting, because the code before the redirect doesn't have the opportunity to set the view locals directly. You could just do:
res.view('login/index', {locals: {flash: {'error':'Wrong Credentials'}}});
and in your template:
<% if((flash = {} || flash) && flash.error){ %>
<div class="row form-row m-l-20 m-r-20 xs-m-l-10 xs-m-r-10">
<div class="alert alert-error">
<button class="close" data-dismiss="alert"></button>
<%- flash.error %>
</div>
</div>
<% }%>
If you were redirecting from another view, then you could use flash messages and keep the same template. In the action you're redirecting from, you'd set a flash message:
req.flash('error', 'my error message');
res.redirect('/someOtherLoginRoute');
and in the action you redirected TO, do:
res.view("login/index", {locals: {flash: req.flash()}});
It's kind of a contrived example, but there you have it.