Best way to populate a javascript typed array?

Question

What is the best way to populate a javascript typed array with literal data?

Recently I've been working a lot with javascript typed arrays for some mathematical work. In particular, I'm using lots of Float32Array objects.

I often have to manually populate their values. With a regular array, there is the following literal syntax available: var a = [0,1,2]; But there seems to be no equivalent way to populate a typed array, so I find I have to do it with lots of individual statements;

var a = new Float32Array(3);
a[0] = 0;
a[1] = 1;
a[2] = 2;

This gets very annoying if there's more than about 4 values. And it seems wasteful too, both in terms of script size, and javascript execution, because it has to interpret all those individual statements.

Another approach I've used is creating a setter function:

var populateArray(a,vals) {
    var N = vals.length;
    for (var i=0; i<N; i++) {a[i]=vals[i];}
};
var a = new Float32Array(3);
populateArray(a,[0,1,2]);

But this seems quite wasteful too. I have to create a regular array as big as the typed array first, to feed into the populateArray function, and then there's the iteration.

So... the question is: Is there a more direct and efficient way to fill a typed array with literal data?

Johan · Accepted Answer · 2014-02-25 15:01:35Z

6

Why not simply do new Float32Array([1,2,3]);

Look at the constructor overloads:

Float32Array Float32Array( unsigned long length );

Float32Array Float32Array( TypedArray array );

Float32Array Float32Array( sequence array );

Float32Array Float32Array( ArrayBuffer buffer, optional unsigned long byteOffset, optional unsigned long length );

answered Feb 25, 2014 at 15:01

Johan

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3 Comments

roberto Over a year ago

or, if the array is already declared, can also use a.set([1,2,3])

Daniel Howard Over a year ago

Wow - I didn't know you could do that! Unbelievably simple. I can't believe I haven't seen that before. Thank you so much!

Johan Over a year ago

@DanielHoward Np. Sometimes it's easier than you think ;)

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