proposal: syscall/js: Add `SetSymbol` method on `js.Value`

[zyxkad]

This method should works as same as js.Value.Set, but it uses Symbol as the key.
It's useful because we can use more js syntax sugar with symbols, such as for ... of, and we don't have to write extra javascripts to wrap them.

A suggestion signature:

func (js.Value)SetSymbol(symbol js.Value, value any)

[ianlancetaylor]

CC @golang/js

[johanbrandhorst]

Thanks for your proposal. Could you elaborate a little on what you have to do today? I'm just trying to understand exactly what the benefit is here. Do you have a practical example which would be greatly simplified with this change? Thanks!

[zyxkad]

yes, so basically, I'm making go channel iterable in js.
When I doing something will use lots time, it's better to return a channel than an array, because I can render the data already processed before all stuffs are done.

Example is at https://github.com/kmcsr/mcla/blob/main/cmds/mcla_wasm/utils.go#L67

[zyxkad]

Without symbols when I want to iter it, I have to call

let value;
while(!({value} = await iter.next()).done){
  /* do something with value */
}

if with iterator symbol, I can use for ... of, it's much simple than while next

for await (let value of iter){
  /* do something with value */
}

[zyxkad]

As you can see, the first example while next is I already compressed, if it should be step by step, then it will be:

while(true){
  let res = await iter.next()
  if(res.done){
    break
  }
  let value = res.value
  /* do something with value */
}

[zyxkad]

@johanbrandhorst Any progress?

[johanbrandhorst]

No one is working on this as far as I know. If you want to work on this, feel free to experiment with it.

[gopherbot]

Change https://go.dev/cl/555417 mentions this issue: syscall/js: add methods GetSymbol, SetSymbol, and DeleteSymbol

[johanbrandhorst]

Thanks for opening a CL, I think this has to go through the proposal review process before we can merge it, but it's a great start! I think this sounds like a reasonable addition to the syscall/js package and you make a compelling case that this provides a significant boost to developer ergonomics without adding much maintenance burden. Could the proposal review committee add this to the next review?