Javascript map weird behavior

Question

I fixed some problems with code objects and tried to convert a string to a list of numbers like this:

"102904".split("").map(parseInt);

The expected result will be something like this:

[1, 0, 2, 9, 0, 4]

But instead, it returns:

[1, NaN, NaN, NaN, 0, 4]

Consider that the card should apply to each item in the list that contains 1-digit strings. One would think that it does not understand correctly, because the database is not used, but:

"102904".split("").map(function(x){ return parseInt(x);});
[ 1, 0, 2, 9, 0, 4]

Use parseInt(x, 10)does not change the result. But sending directly parseInt to the card creates NaN...

I tried Chrome and Firefox and get the same results.

Answer 1

, Array.prototype.map, :

parseInt, radix – . ,

string | base | result
----------------------
1      | 0    | 1
0      | 1    | NaN
2      | 2    | NaN
9      | 3    | NaN
0      | 4    | 0
4      | 5    | 4

, base 0 ( ), 1, NaN. , parseInt 0 :

radix undefined 0 ( ), JavaScript : (MDN docs)

Answer 2

parseInt - radix.

, - map : .

: 0, 2, 9

?

• 0 - radix, 1. 1 , NaN
• 2 - , 2. 2- 2 (0 1 )
• 9 - radix, 3. 9 (0, 1 2 )

Answer 3

"102904".split("").map(function(x, y){ console.log(x, y) });

returns

1 0
0 1
2 2
9 3
0 4
4 5

This means that in the first example it parseIntis called as follows:

parseInt("1", 0);
parseInt("0", 1);
parseInt("2", 2);
parseInt("9", 3);
// ecc...

You pass the iteration index as the second parameter to parseInt()(which is the radius of the number to be analyzed).

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The best solution is to use the second approach with the code already published.