Array.map + parseInt [duplicate]

Question

var timeSplit = timeCaption.innerText.trim().split(' ');
            

will yield an Array of ["10:00", "–", "18:00"]

var startStr = timeSplit[0].split(':');

will yield an Array of ["10", "00"]

var res = startStr.map(parseInt);

will yield an Array of [10, NaN]

however

var res = startStr.map(function (x) {
   return parseInt(x);
});

works correctly and will yield the "expected" Array of [10, 0]

I expect each string to be passed to parseInt which returns the correct interger value (and doing that separately also yields the correct result, just like the working code).

What am I missing here?

Answer 1

parseInt accepts 2 arguments:

1. string to be parsed
2. radix

.map calls your function with 3 arguments:

1. the value
2. the index
3. array

If you think about it,

parseInt("00", 1)

doesn't really make sense and it returns NaN. parseInt accepts radixes between 2 and 36.