" ['1', '7', '11'].map(parseInt);

For what you would expect the output to be:

[1, 7, 11]

However, things get a bit off here, and the actual result is:

[1,NaN,3]

At first, this may look up very weird, but it actually has an elegant explanation. "

The elegant explanation is that JavaScript was taken over by psychopaths like bajcmartinez.

JavaScript is fine for button onClick code. Outside of that it's garbage.