Passing a frozen object as config object generates `Cannot assign to read only property 'origin' of object` TypeError

[saadtazi]

Passing a frozen object as config object generates `Cannot assign to read only property 'origin' of object` TypeError

[LinusU]

I think that it's generally considered bad practice to modify objects passed to your function. We should try and fix this 👍 A PR would be great

[saadtazi]

Thank you for the quick reply. I can give it a try this week I think.

Object.assign is not defined in node 0.10 (it appeared in node 4 I think).

So do you have a preferred way of doing it?

1. Knowing the list of the possible option properties (currently 8), manually copy those properties at the beginning of cors()

var allowedProperties = ['origin', ...]; 

// ... in cors
function cors(opts, req, res, next) {
   var options = {};
  allowedProperties.forEach(function (prop) {
    options[prop] = opts[prop];
  });
  //...
})

2. copy an Object.assign polyfilll like this one in the project (no new dependency
3. add an Object.assign polyfill package

Those proposed options assume that "sub-properties" are not altered (I quickly checked, it seems to be the case...).

I am inclined to go with option 3, but I don't know if you guys want to limit the number of dependencies.

[LinusU]

I personally think that approach 3 is the best one :)