在 2016/9/28 22:59, Danielle McLean 写道:
From: 段垚 (mailto:[email protected])
Date: 28 September 2016 at 16:36:52
[I]mplementors warn that mutating prototype causes "performance
hazards".
You don't actually need to mutate any prototypes to get prototypeless
objects out of `JSON.parse` - the reviver function is allowed to
return a new object instead, so you can create a fresh one with the
correct prototype. For example:
```js
JSON.parse(string, function(k, v) {
if (v && typeof v === 'object' && !Array.isArray(v)) {
return Object.assign(Object.create(null), v);
}
return v;
});
```
Yes, but creating a copy also has performance penalty. This proposal is made
for performance.
How about adding an option to omit prototype of objects created by
JSON.parse()?
JSON.parse(str, { noPrototype: true });
While you can achieve the appropriate result already without extra
language support, I think this particular situation is common enough
that such an option might be a good idea.
How would you expect this new parameter to interact with the existing
second parameter to `JSON.parse`, the reviver function? I'd suggest
that the cleanest way to add the options would be for the second
parameter to be either an object or function, like this:
```js
JSON.parse(str, someFunc);
// equivalent to
JSON.parse(str, {reviver: someFunc});
```
Looks reasonable.
Maybe we can simply add another method, say
`JSON.parseWithoutPrototype()`. This makes feature detection easier.
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