Use Object.defineProperty

[jordanbtucker]

Properties should be set with Object.defineProperty to maintain backward compatibility with JSON.parse.

Currently JSON5 exhibits the following behavior.

    JSON.parse(`{"__proto__": 1}`)
//  {__proto__: 1}
    JSON5.parse(`{"__proto__": 1}`)
//  {}

However, when JSON5 uses Object.defineProperty instead of object[key] = value to set the properties of objects, it maintains backward compatibility.

Fixes #199

[jordanbtucker]

The question is, is this a major, minor, or patch version bump?

[LongTengDao]

What do you mean for:

However, when JSON5 uses Object.defineProperty instead of object[key] = value to set the properties of objects, it maintains backward compatibility.

[jordanbtucker]

@LongTengDao Before this PR, JSON5 sets object properties by using the syntax object[key] = value.

This is a problem for the special property __proto__ because it is not enumerable or writable. In other words, object['__proto__'] = value has no effect.

However, if you use Object.defineProperty, then you can create a new __proto__ property that is enumerable and writable and hides the original __proto__ property. This is how JSON does it (via CreateDataProperty), and that's what this PR implements.

[LongTengDao]

This is a problem for the special property __proto__ because it is not enumerable or writable. In other words, object['__proto__'] = value has no effect.

__proto__ is a getter/setter on Object.prototype. It only ignore setting primitive value (exclude null). If set object or function to it, there is side effect (but be proto, not property, which not expected here).

When would this PR be released?

[jordanbtucker]

Merged in 4a8c456