Array.prototype[0] setter

David Bruant bruant.d at gmail.com
Sat Oct 22 09:45:10 PDT 2011


Are there tests for this?

David

Le 18/10/2011 21:37, Allen Wirfs-Brock a écrit :
> On Oct 18, 2011, at 12:31 PM, felix wrote:
>
>> If I define a setter for Array.prototype[0], does [].push invoke that setter?
> It's supposed to.
>
>> Test code:
>>
>> <!doctype html><html><body>
>> <script>
>>  Object.defineProperty(
>>    Array.prototype, 0,
>>    { get : function() { alert('get 0'); return this.zero; },
>>      set : function(v) { alert('set 0 ' + v); this.zero = v; },
>>      enumerable : true,
>>      configurable : false });
>>  var a = [];
>>  alert('before push a[0] = ' + a[0]);
>>  a.push(44);
>>  alert('after push a[0] = ' + a[0]);
>> </script>
>> </body></html>
>>
>> On all the browsers I've tried so far, the setter doesn't get invoked.
>>
>> However, it looks to me like the ES5.1 spec says the setter should get invoked:
> Yes, that is what it says and it is intentional.
>
>> 15.4.4.7 says push() invokes the [[Put]] internal method
>>
>> 8.12.5 says [[Put]] tries to use an inherited property descriptor if
>> there isn't an own property descriptor.
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>>
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