parseInt() parses number literals with exponent incorrectly

Question

I have just observed that the parseInt function doesn\'t take care about the decimals in case of integers (numbers containing the e character).

Answer 1

If the parsed string (stripped of +/- sign) contains any character that is not a radix digit (10 in your case), then a substring is created containing all the other characters before such character discarding those unrecognized characters.

In the case of -3.67394039744206e-15, the conversion starts and the radix is determined as base 10 -> The conversion happens till it encounters '.' which is not a valid character in base 10 - Thus, effectively, the conversion happens for 3 which gives the value 3 and then the sign is applied, thus -3.

For implementation logic - http://www.ecma-international.org/ecma-262/5.1/#sec-15.1.2.2

More Examples -

alert(parseInt("2711e2", 16));
alert(parseInt("2711e2", 10));

TO note:

The radix starts out at base 10.

If the first character is a '0', it switches to base 8.

If the next character is an 'x', it switches to base 16.