Why? console.log(parseFloat(1024) + parseFloat(300.86)); = 1324.8600000000001

[iceopen]

console.log(parseFloat(1024) + parseFloat(300.86));
console.log(parseFloat(100) + parseFloat(100.86));
console.log(parseFloat(1024) + parseFloat(200.78));
console.log(parseFloat(400) + parseFloat(200.86));
var tol = parseFloat(1024) + parseFloat(300.86);
console.log(tol);

1324.8600000000001
200.86
1224.78
600.86
1324.8600000000001

[mscdex]

Welcome to the world of floating point math. There are lots of articles that describe how floating point in general works. You might start with the answers from this stackoverflow question.

[iceopen]

I tested the pull 3 programming languages:
Java:1324.8600000000001
Node:1324.8600000000001
PHP:1324.86

[bnoordhuis]

Closing, not a bug. Like @mscdex said, that's how floating point values work; 1324.86 is a value that cannot be exactly represented in a binary IEEE-754 double.

PHP has the same issue by the way, it's just that the way it prints floating point numbers by default doesn't show it:

$ php -r 'printf("%.16f\n", 1024.0 + 300.86);'
1324.8600000000001273

One language that does get it right is perl6:

$ perl6 -e 'printf "%.16f\n", 1024.0 + 300.86'
1324.8600000000000000

That's because it represents the number as a nominator/denominator rational:

$ perl6 -e 'print "{(1024.0 + 300.86).nude}\n"'
66243 50

The more you know, right?