How are numbers represented in binary in JavaScript

Question

I'm creating a tutorial on JavaScript, and as I deal with explaining bitwise operators, etc. How negative numbers are represented in JavaScript keep coming up.

I believe all I need to describe in my tutorial is two's complement, but do I also need to describe one's complement, or is one's complement irrelevant in JavaScript?

How about floating point numbers, positive and negative numbers, in JavaScript?

All numbers in JS use IEEE 754 64-bit floating point representation, so even x = 4 is a float. However, bitwise operators forcefully convert a number to 32-bit integer, so 3.14 | 0 will produce 3 but also (2 ** 31 - 1) | 0 is 2147483647 yet (2 ** 31) | 0 is -2147483648. — VLAZ
– VLAZ, Commented Nov 27, 2020 at 5:59
The bit string of any float can be obtained with Array.from(new Uint8ClampedArray(new Float64Array([ 420.69 ]).buffer), (byte) => byte.toString(2).padStart(8, "0")).join(""). Replace Float64Array by Int32Array to inspect integers. The bytes may, however, be reversed, based on endianness. — Sebastian Simon
– Sebastian Simon, Commented Nov 27, 2020 at 13:15

zmag · Accepted Answer · 2020-11-27 06:16:45Z

2

All numbers in JavaScript are floating point numbers. The representation rule for negative numbers is the same as IEEE-754.

But when you are using bitwise operators in JavaScript, The operands are converted to signed 32-bit integers automatically.

answered Nov 27, 2020 at 6:16

zmag

8,27112 gold badges39 silver badges47 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Greg Lafrance Over a year ago

Are those 32-bit integers represented in two's complement?

zmag Over a year ago

@GregLafrance I believe so.

Collectives™ on Stack Overflow

How are numbers represented in binary in JavaScript

1 Answer 1

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related