floating point - Encoding and decoding IEEE 754 floats in JavaScript - Stack Overflow

admin管理员组

文章数量:1363053

I need to encode and decode IEEE 754 floats and doubles from binary in node.js to parse a network protocol.

Are there any existing libraries that do this, or do I have to read the spec and implement it myself? Or should I write a C module to do it?

I need to encode and decode IEEE 754 floats and doubles from binary in node.js to parse a network protocol.

Are there any existing libraries that do this, or do I have to read the spec and implement it myself? Or should I write a C module to do it?

• javascript
• floating-point
• node.js
• ieee-754

Share Improve this question Follow asked Sep 18, 2010 at 8:10 nornagonnornagon 15.8k1818 gold badges7676 silver badges8686 bronze badges 2

• 1 Maybe you can see if this thing does what you want: jsfromhell./classes/binary-parser – Tor Valamo Commented Sep 18, 2010 at 20:39
• See also: javascript - Read/Write bytes of float in JS - Stack Overflow (all the answers there would work here too) – user202729 Commented Jan 30, 2021 at 10:55

Add a ment  | 

3 Answers 3

Sorted by: Reset to default 3

Note that as of node 0.6 this functionality is included in the core library, so that is the new best way to do it.

See http://nodejs/docs/latest/api/buffer.html for details.

If you are reading/writing binary data structures you might consider using a friendly wrapper around this functionality to make things easier to read and maintain. Plug follows: https://github./dobesv/node-binstruct

In modern JavaScript (ECMAScript 2015) you can use ArrayBuffer and Float32Array/Float64Array. I solved it like this:

// 0x40a00000 is "5" in float/IEEE-754 32bit.
// You can check this here: https://www.h-schmidt/FloatConverter/IEEE754.html
// MSB (Most significant byte) is at highest index
const bytes = [0x00, 0x00, 0xa0, 0x40];
// The buffer is like a raw view into memory.
const buffer = new ArrayBuffer(bytes.length);
// The Uint8Array uses the buffer as its memory.
// This way we can store data byte by byte
const byteArray = new Uint8Array(buffer);
for (let i = 0; i < bytes.length; i++) {
  byteArray[i] = bytes[i];
}

// float array uses the same buffer as memory location
const floatArray = new Float32Array(buffer);

// floatValue is a "number", because a number in javascript is a
// double (IEEE-754 @ 64bit) => it can hold f32 values
const floatValue = floatArray[0];

// prints out "5"
console.log(`${JSON.stringify(bytes)} as f32 is ${floatValue}`);

// double / f64
// const doubleArray = new Float64Array(buffer);
// const doubleValue = doubleArray[0];

PS: This works in NodeJS but also in Chrome, Firefox, and Edge.

I ported a C++ (made with GNU GMP) converter with float128 support to Emscripten so that it would run in the browser: https://github./ysangkok/ieee-754

Emscripten produces JavaScript that will run on Node.js too. You will get the float representation as a string of bits, though, I don't know if that's what you want.

本文标签： floating pointEncoding and decoding IEEE 754 floats in JavaScriptStack Overflow