How to cast a normal array to a Float32Array?

Question

I've found many ways to create a Float32Array from an array, but all of them involve copying all elements. I want to avoid that cost, because the array will never be used again. I just want to cast it. How is that possible?

Check this answer and flip the implementation around? stackoverflow.com/questions/12760643/… — Kyle Pittman
– Kyle Pittman, Commented Jun 6, 2014 at 0:43
No, this answer involves making a whole new copy of the array. — MaiaVictor
– MaiaVictor, Commented Jun 6, 2014 at 0:48
I don't think you can just "cast" it as they are likely different data structures since a normal array can contain any type of element, not just numbers so JS has to include some type info in a normal array element. The info in the answer Kyle references just uses .slice() to do a copy. — jfriend00
– jfriend00, Commented Jun 6, 2014 at 1:00
This is a conversion operation; as such the result (in either direction) is a new array/object, even if the loop is hidden by some function. Unlike a per-item conversion (e.g. Array of number -> Array of string), a Float32Array object is represented by a specialized implementation and separate from any standard Array/object, which is why the entire array itself must be "new". — user2864740
– user2864740, Commented Jun 6, 2014 at 1:05

Bergi · Accepted Answer · 2014-06-06 02:11:57Z

12

It's impossible. A Float32Array is always a different object than a normal array.

If you want to avoid the cost of copying the items, a) don't use a normal array in the first place or b) let your function that uses it work with normal arrays as well.

If you are looking for the "casting" operation, you can just invoke the Float32Array constructor with the normal array:

var arr = [0.3, 1, 2];
var typedArr = new Float32Array(arr);

edited Jun 6, 2014 at 2:11

answered Jun 6, 2014 at 2:06

Bergi

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