在 2016/9/29 0:04, Michał Wadas 写道:
Have you ever encountered performance issue because of copying object
on deserialization?
Not yet.
https://gist.github.com/Ginden/381448a17f50c7669b9a3693742e3a3d For me
results are:
Simple JSON.parse, 100000 iterations: 39.594999999997526ms
JSON.parse with copy, 100000 iterations: 184.5699999999997ms
JSON.parse with __proto__ change, 100000 iterations: 89.75500000000102ms
Thanks for writing this test. I got similar result on Firefox; while on
Chrome and Edge, there is not much difference between coping and
changing __proto__ .
However, it is not easy to messure overhead of GC after copy and the
effect of __proto__ change on property access performance.
On Wed, Sep 28, 2016 at 5:49 PM, 段垚 <[email protected]
<mailto:[email protected]>> wrote:
在 2016/9/28 22:59, Danielle McLean 写道:
From: 段垚 (mailto:[email protected] <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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