For anyone who is wondering why: parseInt() only accepts strings as input. So JavaScript calls .toString() on the number before passing it as an argument.

For anyone who is wondering why: parseInt() only accepts strings as input. So JavaScript calls .toString() on the number before passing it as an argument. (0.000001).toString() // "0.000001" (0.0000001).toString() // "1e-7" By the way, TypeScript or Flow would have caught this error during compile time.