Yeah - not being aware of this will screw you up!
['10','10','10','10','10'].map(parseInt)
// [10, NaN, 2, 3, 4] ['10','10','10','10','10'].map(parseInt)
// [10, NaN, 2, 3, 4] parseInt('10', {test: 'test'})
10
parseInt('10', 'test')
10
parseInt('10', '2')
2