ejs 网站从服务器端获取了一个变量，并且无法正常工作

Question

I use Node.js, express and ejs

Client got a variable from server side

res.render('Messagess.ejs', {friendsdatas:friends, myaccount:accresult, mytoken:cookies.LoginToken})

I use this variable in html code like this. This working properly.

<% for (var i=0; i<friendsdatas.length; i++) { %>
  <p class="name"><%= friendsdatas[i].Username %></p>
<% } %>

But inside the script section, I can't use like how I want

for (var i = 1; i<'<%=friendsdatas.length %>'; i++) {
  console.log('<%=friendsdatas[i].id %>')
}

Here I got error Error

If I use the variable like this, that working properly

console.log('<%=friendsdatas[1].id %>')

Answer 1

For this case,

<% for (var i=0; i<friendsdatas.length; i++) { %>
  <p class="name"><%= friendsdatas[i].Username %></p>
<% } %>

code that is inside <% %> is executed by server. Since the control structure (for) is inside <% %>, it can run and read friendsdatas .

However, the other case

for (var i = 1; i<'<%=friendsdatas.length %>'; i++) {
  console.log('<%=friendsdatas[i].id %>')
}

This for part is run by the client side. The client side can't access friendsdata.id so it can't be run.

<% for (var i = 1; i<'<%=friendsdatas.length %>'; i++) { %>
  console.log('<%=friendsdatas[i].id %>')
<% } %>

This will output i console.log statement. Or alternatively

<% 
let friendsdatasString = JSON.stringify(friendsdatas);
%>
<script>
let friendsdatas = <%- friendsdatasString %>;
for (var i = 1; i<friendsdatas.length; i++) {
  console.log(friendsdatas[i].id)
}
</script>

Pass the server side variable to client side variable and loop normally for client side.