Undesirable long number rounding in Chrome

Question

How can it be possible, Chrome flooring the last 1 in a long number:

var a = 12345678987654321;
console.log("a =",a); // Traces: 12345678987654320 

Fiddle: http://jsfiddle.net/zAXLx/

Answer 1

All numbers in JavaScript are IEEE-754 double-precision numbers, which have a maximum number of ~15 significant digits. It's not Chrome, it's the nature of IEEE-754 double-precision floating point. When numbers get really big like that, they start becoming imprecise.