Map.prototype.clear method

Yehuda Katz wycats at
Mon Oct 22 10:58:17 PDT 2012

A clear method is definitely important for both Map and Set. Our real-world
polyfills have also needed them.

What about copying of these new data structures?

On Mon, Oct 22, 2012 at 10:40 AM, Brendan Eich <brendan at> wrote:

> +1, no brainer. Thanks for supplying the brain!
> /be
> Jason Orendorff wrote:
>> An actual real-world user of ES6 Map (in Firefox-only code) is asking
>> for a .clear() method:
>> <jcranmer>  I'm writing a mork reader in JS for mconley's new
>> addressbook (using JS workers, OS.File, and JS Maps !)
>> <jcranmer>  one of the operations I need to be able to do amounts to
>> "clear the entire table"
>> <jcranmer>  I can't just make it a new map, since I put other
>> properties on the map that I don't want to lose
>> <jcranmer>  I'm doing this for now:
>> <jcranmer>        for (let [tid, value] of this._currentTable)
>> <jcranmer>          this._currentTable.delete(tid)**;
>> <jorendorff>  why store those extra properties on this._currentTable
>> rather than directly on this?
>> <jcranmer>  because I have multiple tables
>> In our current implementation, a builtin Map.prototype.clear method
>> that simply removes all entries from the Map would be quite a bit
>> faster than what jcranmer is currently doing.
>> -j
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Yehuda Katz
(ph) 718.877.1325
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