Reference an object, based on a variable with it's name in it

Question

Reference an object, based on a variable with it's name in it

I'm looking for a way to reference an object, based on a variable with it's name in it. I know I can do this for properties and sub properties:

var req = {body: {jobID: 12}};
console.log(req.body.jobID);             //12

var subProperty = "jobID";
console.log(req.body[subProperty ]);     //12

var property = "body";
console.log(req[property][subProperty]); //12

is it possible for the object itself?

var req = {body: {jobID: 12}};
var object = "req";
var property = "body";
var subProperty = "jobID";
console.log([object][property][subProperty]); //12

or

console.log(this[object][property][subProperty]); //12

Note: I'm doing this in node.js not a browser.

Here is an exert from the function:

        if(action.render){
            res.render(action.render,renderData);

        }else if(action.redirect){
            if(action.redirect.args){
                var args = action.redirect.args;
                res.redirect(action.redirect.path+req[args[0]][args[1]]);

            }else{
                res.redirect(action.redirect.path);
            }
        }

I could work around it by changing it to this, but I was looking for something more dynamic.

        if(action.render){
            res.render(action.render,renderData);

        }else if(action.redirect){
            if(action.redirect.args){
                var args = action.redirect.args;
                    if(args[0]==="req"){
                        res.redirect(action.redirect.path+req[args[1]][args[2]]);
                    }else if(args[0]==="rows"){
                        rows.redirect(action.redirect.path+rows[args[1]][args[2]]);
                    }
            }else{
                res.redirect(action.redirect.path);
            }
        }

javascript
node.js

Answer 1

Normally it's impossible to reference an object by its name. But since you have only two possible candidates...

var args, redirect_path = '';
if(args = action.redirect.args) {
    try {
        redirect_path = ({req:req,rows:rows})[args[0]][args[1]][args[2]];
    } catch (_error) {}
}
res.redirect(action.redirect.path + (redirect_path || ''));

I'm using inline object {req:req,rows:rows} as a dictionary to lookup for args[0] value.

I wrapped the whole construction with try ... catch, because it's dangerous. For example, passing anything except 'req' or 'rows' as args[0] will result in an exception being thrown.

I also moved res.redirect outside of if to clarify the code.

Update

It's also possible to use args array with arbitrary length. But to do so you'll need to loop through args array:

var branch, redirect_path;
if (action.redirect.args) {
  try {
    branch = { req: req, rows: rows }
    action.redirect.args.forEach(function(key) {
      branch = branch[key];
    });
    if ('string' === typeof branch) {
      redirect_path = branch;
    }
  } catch (_error) {}
}
res.redirect(action.redirect.path + (redirect_path || ''));

A added 'string' === typeof branch check to ensure that the resulting value is a string.