Javascript将Uint8Array [x]分配给新的var：类型？

Question

If I have the following code:

var uInt8Array = new Uint8Array([0, 1, 2]);
var number = uInt8Array[1];

Will number be parsed to a 64-bit float or will it stay a 8-bit unsigned integer?

Answer 1

The Uint8Array datatype exists for the purpose of saving memory in some specific case. The savings in memory are fairly unimportant when dealing with single elements, but become important when dealing with large arrays, since each element will consume 1/8th the memory that it would normally.

Examples where this becomes important are when dealing with media, ie audio,images and video.

A 1 mega-pixel image will be stored as 4 million elements, each of 8bits. 8bits for each of r, g, b and a. This will of course, consume 4,000,000 bytes. If this datatype did not exist and images were still stored in arrays with 4 elements, this memory requirement would balloon-out to 32,000,000 bytes.

You can test this yourself by writing a simple test-code and placing watches on the variables. The initial array is shown to be a Uint8Array, while the element extracted from it is shown to be a standard number object.

Here's a screen-shot of the code you present and the variables in a watch window.