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Trudy
Trudy

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['10','10','10','10','10'].map(parseInt) what&why?

the answer is [10, NaN, 2, 3, 4]

['10','10','10','10','10'].map(parseInt) is equal

['10','10','10','10','10'].map((item, index) => parseInt(item, index))

here is detail about parseInt

Top comments (2)

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tracygjg profile image
Tracy Gilmore •

Hi Trudy,

Your second example ['10','10','10','10','10'].map((item, index) => parseInt(item, index)) is not quite correct.

['10','10','10','10','10'].map(parseInt);
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is actually equivalent to

['10','10','10','10','10'].map((item, index, arr) => 
  parseInt(item, index, arr));
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but parseInt actually only expects two parameters so the third argument is ignored. This is because the map method expects a callback with three parameters. See

Regards, Tracy

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Trudy •

You explained very well, more detailed and specific，thank you

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