About the binary format of JavaScript TypedArray float32

The Float32Array will internally represent the values bases on the endianess of the host system, typically little-endian.

And yes, the format is IEEE 754 (this has been around since before FPUs came along, and the variations of it deals with more the width, ie. 64-bit, 80-bit and so on). All numbers (Number) in JavaScript is internally represented as 64-bit IEEE 754. For typed arrays both 32-bit and 64-bit IEEE 754 is of course available.

PowerPC and 68k CPUs uses big-endian (the way it ought to be! :) ). The so-called network order is also big-endian, and many platform-independent file formats are stored in big-endian byte order (in particular with audio and graphics). Most mainstream computers uses little-endian CPUs such as the x86. So in cases with a combination of these you very likely have to deal with different byte orders.

To deal with endianess you can instead of using a Float32Array use a DataView.

For example:

var buffer = new ArrayBuffer(10240);    // some raw byte buffer
var view = new DataView(buffer);        // flexible view supporting endianness

Now you can now read and write to any position in the buffer with endianess in mind (DataView also allow reading/writing from/to non-aligned positions, ie. you can write a Float32 value to position 3 if you need to. You cannot do this with Float32/Uint32/Int16 etc.).

The browser will internally convert to the correct order - you just provide the value as-is:

view.setFloat32(pos, 0.5);              // big-endian
view.setFloat32(pos, 0.5, false)        // big-endian
view.setFloat32(pos, 0.5, true);        // little-endian

And likewise when reading:

var n = view.getFloat32(pos);           // big-endian
var n = view.getFloat32(pos, false)     // big-endian
var n = view.getFloat32(pos, true);     // little-endian

Tip: You can use a native Float32Array internally and later read/write to it using endianess. This tend to be speedier but it requires a conversion using DataView at the end if the resulting buffer's endianess is different from the host system:

var f32 = new Float32Array(buffer);     // or use a size
f32[0] = 0.5;

Then to make sure you have big-endian representation:

var view = new DataView(f32.buffer);
var msbVal = view.getFloat32(0):        // returns 32-bit repres. in big-endian

Hope that gave some inputs! Just throw me questions about it if you want me to elaborate on some part.