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JavaScript uses binary64 or double precision. As the former name indicates, numbers are stored in a binary format, in 64 bits. These bits are allotted as follows: The fraction occupies bits 0 to 51, the exponent occupies bits 52 to 62, the sign occupies bit 63.
The JavaScript Number type is a double-precision 64-bit binary format IEEE 754 value, like double in Java or C#.
JavaScript uses double-precision (64-bit) floating point numbers. 64 bits are 8 bytes, but each number actually takes up an average of 9.7 bytes.
JavaScript Numbers are Always 64-bit Floating Point JavaScript numbers are always stored as double precision floating point numbers, following the international IEEE 754 standard.
I'm reading the Number Type section of the book Professional JavaScript for Web Developers. It seems to say that all ECMAScript numbers are binary64 floating point, which is corroborated by this MDN article. But the book author also says:
Because storing floating-point values uses twice as much memory as storing integer values, ECMAScript always looks for ways to convert values into integers.
I expected numbers to each occupy the same amount of memory: 64 bits. And the MDN article says, "There is no specific type for integers". Anyone know what the book author meant? How can integers take up less memory when they're stored as 64-bit floats (if I have that right)? You'll find the whole section at the link above (free sample of the book).
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