Express，如何将变量从路由传递到客户端的JS文件

Question

I have an Express project that has client-side javascript in a separate file that generates a graph. I am trying to pass variables from the express routes to this javascript file so the graph can be drawn. I have tried the code below but I am getting following error.

Error: Cannot find module 'js'

app.get('/users', function(req, res) {
  res.render(path.join(__dirname, '../views/js/users_chart.js'), {
    'users': users
  });
});

Answer 1

I think it'd be helpful for you to review the Express documentation for res.render and serving static files

You can't render JS files.

It appears you want to serve your static user_chart.js with

/* server.js */
app.set('view engine', 'ejs');
app.register('.html', require('ejs'));
// serve your js statically
app.use('/js', path.join(__dirname, '../views/js/users_chart.js')
app.get('/users', function(req, res) {
    // pass variable to html page
    res.render('users.html', {
        'users': users
    });
});

// in users.html
<script type="text/javascript" src="/js/users_chart.js">

This post is probably helpful as well

Answer 2

After receiving great help, found out a solution.

In order to have a javascript file in the client side that would receive the variable from the routes, I had to send the variable in JSON from the routes file to the javascript file the client side. I used XMLHttpRequest in order to receive the JSON in the javascript file of the client side.

Bellow is the code for users_graph.js which is the client side javascript file.

var xmlhttp = new XMLHttpRequest();
var url = "/users";
xmlhttp.onreadystatechange = function() {
    if (xmlhttp.readyState == 4 && xmlhttp.status == 200) {
        var users = JSON.parse(xmlhttp.responseText).users;   
        // do something with the users variable that was passed by the routes

    }
};

xmlhttp.open("GET", url, true);
xmlhttp.setRequestHeader('Accept', 'application/json');
xmlhttp.send();