The extra args passed by map coupled with the optional extra args in standard methods is the cause of a lot of confusion, but this feels like a missed opportuni

The extra args passed by map coupled with the optional extra args in standard methods is the cause of a lot of confusion, but this feels like a missed opportunity for demonstrating functional programming. In the end author suggests ['1', '7', '11'].map(numStr => parseInt(numStr)); I think you'd learn something much more useful with function radixParser(radix) { return numStr => parseInt(numStr, radix); } ['1', '7', '11'].map(radixParser()); > [ 1, 7, 11 ] ['1', '7', '11'].map(radixParser(8)); > [ 1, 7, 9 ] ['1', '7', '11'].map(radixParser(2)); > [ 1, NaN, 3 ]