Where should I define JS function to call in EJS template

Create common functions in js file helper.js.

function common1() {
    //function body
}
function common2(key) {
    //function body
}
module.exports = {
    common1: common1,
    common2: common2
}

And then require this file in your node function

var helper = require('./helper');

and then pass this helper with ejs render

res.render('index', { helper:helper });

And use your function is ejs file

<%= helper.common1() %>

That's It

Just posting this answer here for someone who would might end up on this question while resolving same issue.

All you have to do is create new file (say functions.ejs) and include it in the .ejs file where you want to call that function. So, I have function like this in file named functions.ejs:

<%
getPriceChgArrow = function(value) {
    arrow_img_name = "";
    if (value < 0) {
        arrow_img_name = "arrow_down12x13.gif";
    }
    else {
        arrow_img_name = "arrow_up12x13.gif";
    }
    return arrow_img_name;
}
%>

Then include functions.ejs into the file you want to call function from. Say, I want to call this function in quote.ejs file. So, I would include it as follows:

<% include *file_path*/functions %> 

Just use this function at appropriate location in your ejs file from where you want to call it. For example:

<img src = "http:/some_url/<% getPriceChgArrow(data_point[0].value) %>" />

and you are all set. Hope this helps someone.

Well, for some reason the accepted answer didn't worked out for me. Also it doesn't makes sense to create a separate *.ejs file for each of my functions and then importing the file in view - specially when I have very simple logic to be implemented.

In fact it is very simple and easy to define function and use it in the view

I did this:

<%
   // ------ Define a function
   get_tree = function(tree){
      for(var i in tree){
%>
     <%= tree[i].title %>
<%
      }
   }
  // ----- Call the above declared function
  get_tree(tree);
%>

And it works!

Thanks

You can just require a separate file and set app.locals to this

app.locals = require('./path/helpers')

In helpers.js:

getFlag = function(country) {
var flag_img_name = "";
if (country.toLowerCase() == "us") {
    flag_img_name = "flag_us16x13.gif";
}   
else if (country.toLowerCase() == "ca"){
    flag_img_name = "flag_ca16x13.gif";
}
return flag_img_name; 
}
anotherFunction=function(x){
return 'hello '+x
}

   module.exports={getFlag, anotherFunction}