如何从node.js中的变量传递玉器中的图像源

Question

This is my code from my index.js file (using express for routing)

var express = require('express');
var router = express.Router();

/* GET home page. */
router.get('/', function(req, res){
   var db = req.db;
   var collection = db.get('usercollection');
   var source = req.app.get('imgSource');
   console.log("IMG SOURCE: " + source);
   collection.find({},{},function(e,docs,source){
     res.render('index',{
      "userlist" : docs,
      "imgURL" : source,
      "title": "Insta-Famous"
     });
   });
});

module.exports = router;

And this is my code from my index.jade

extends layout

block content
 h1= title
 p Welcome to #{title}
 ul
  each user, i in userlist
    li
        p #{user.instaid}
        p #{user.price}
    li
        img(src = "#{imgURL}")

source is a variable that is defined in app.js and then used in my index.js file. I know this variable has a value because it prints to console.log when I start my application. However the image does not load and instead displays a 404 question mark.

If I copy and paste the image source (which is: http://naccrra.org/sites/default/files/default_site_pages/2013/instagram-icon.png ) then the image loads fine.

What am I doing wrong here?

Thank you in advance for your help.

Answer 1

You were accepting an argument with the same name that the varible from outer scope has and which you intended to use - source

var source = req.app.get('imgSource');
collection.find({},{},function(e,docs,source){
 ...
});

Any named argument to a function takes precedence over the same name variable of the outer scope. For example:

var a = 1;
var b = 2;
function fn(a){
    a //=> 'precedence'
    b //=> 2
}
fn('precedence');

If no variable was passed when calling, but the definition still takes a named argument, that argument will automatically be undefined , which is what was happening in your case. collection.find 's callback is only ever called with two arguments - e and docs , any sunsequent arguments if named would have been set to undefined

You simply needed not take that extra named argument, which was unnecessary in the first place.

var source = req.app.get('imgSource');
collection.find({},{},function(e,docs){
 ...
});