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Narrow types when using Array.filter #2835

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Narrow types when using Array.filter#2835
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SuggestionAn idea for TypeScriptToo ComplexAn issue which adding support for may be too complex for the value it adds

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@NoelAbrahams
Noel Abrahams (NoelAbrahams)
opened on Apr 20, 2015

Hi,

Will this be possible?

var foo: (number|string)[] = [1, 'bar'];

foo.filter(item => typeof item ==='string').map(item => item/*string type*/);
foo.filter(item => typeof item !=='string').map(item => item/*number type*/);

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  1. Ryan Cavanaugh (RyanCavanaugh)
    added
    SuggestionAn idea for TypeScript
    Too ComplexAn issue which adding support for may be too complex for the value it adds
    on Apr 20, 2015

  2. RyanCavanaugh commented on Apr 20, 2015

    @RyanCavanaugh
    Ryan Cavanaugh (RyanCavanaugh)
    on Apr 20, 2015
    Member

    Not happening unless someone can figure out a reasonable way to write a signature for filter in a way that is generalizable.

  3. Ryan Cavanaugh (RyanCavanaugh)
    closed this as completedon Apr 20, 2015
  4. microsoft
    locked and limited conversation to collaborators on Jun 18, 2018
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