For better results start at -1 '-1 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20'.split(' ').map(parseInt) gets you [ -1, NaN, // could be bet

For better results start at -1 '-1 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20'.split(' ').map(parseInt) gets you [ -1, NaN, // could be better 1, 2, 3, 4, 5, 6, 7, 8, 9, // ok a little bumpy at the start but now we're cookin' 11, 13, 15, 17, 19, 21, 23, 25, 27, 29, // not great not terrible 42 // dang ] way closer. Pretty sure the Number constructor was made to get you around this. map(Number) does what you would expect.