Typed Arrays in ECMAScript 6

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27 points·madflame991··6 comments

Typed Arrays are not the most exciting part of ECMAScript 6, but it is still good that they are part of the language now (vs. only a browser API). What surprised me while researching the post was how many browser APIs support Typed Arrays for binary data: File API, XMLHttpRequest, Fetch API, Canvas, WebSockets, WebGL, Web Audio API, and others.

(Disclaimer: I’m the author of the blog post.)

Are typed arrays stored outside of the JS heap? For example, in node.js you can use Buffers to get around V8's 1.8GB JS heap limit -- are typed arrays similar? Does the ES6 spec specify whether typed arrays should be stored separately from the JS heap, or is that an implementation detail?

Yes, that is left unspecified in the spec:

* http://www.ecma-international.org/ecma-262/6.0/#sec-allocate... (relevant: step 4, CreateByteDataBlock())

I use typed arrays in Python when I need to store a lot of data in memory, and the overhead of objects would be too large (for example I built a little library that can load a country's worth of openstreetmap data).

What I really miss is typed dictionaries (int -> int).

I don’t think there’ll ever be typed dictionaries (which are a fairly high-level data structure). There is, however, a proposal for typed objects: https://github.com/dslomov/typed-objects-es7

Well, one could build a typed object-array library using typed arrays (i.e. use one typed array for every member). This actually gives me an idea... :P

But you wouldn't want to rebuild a dict using integer arrays, that would be pretty slow.

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