Pipeline or temporary var storage?

[stephaneraynaud]

Pipeline operator general purpose is to obtain better readability from chain3(chain2(chain1(value))) to value |> chain1 |> chain2 |> chain3.

Currently, without pipeline operator, we can do something like:

let value;
let chained1 = chain1(value);
let chained2 = chain2(chained1);
let chained3 = chain3(chained2);

From my understanding, pipe is about putting something into a temporary var and using this var later in the same expression.

Pipe is something about:

set(value) then
set(chain1(get())) then
set(chain2(get())) then
chain3(get())

Why not think about an operator whose global purpose would be to set a var into a temp variable then reusing it later?

Note: i'm using ↑ for set, ↓ for get and , for then, but it may not be the best proposal.

// Value is stored, then the stored value is checked.
let visible = value↑, (↓ != null && !↓.hidden);

pipeline would be:

value↑, chain1(↓)↑, chain2(↓)↑, chain3(↓);

we can store variable at any time:

// Value is stored and used inside doSomethingWithValue
let something = console.log(array.filter(value↑)), doSomethingWithValue(↓ * 2); 

and why not imagine storing vars with identifiers:

let myFilteredArray = myParameters↑p, anArray↑a, ↓a.filter(↓p);

It may be even more applications to such an operator.

It may seems to be a lot like the pipeline operator, but the purpose of this issue is to think wider about an operator that could be used in a less constrained way.
What do you think?

[js-choi]

If you’re doing nested explicit variable bindings, then do expressions would be usable here, wouldn’t they?

let myFilteredArray = do { const p = myParameters, a = anArray; a.filter(p) };

[stephaneraynaud]

This
#95
and
https://github.com/gilbert/proposal-temporary-bindings
and
#89 (comment)
is quite related to what I proposed.

[tabatkins]

Closing this issue, as the proposal has advanced to stage 2 with Hack-style syntax. Also, see https://github.com/tc39/proposal-pipeline-operator/blob/master/README.md#temporary-variables-are-often-tedious for a more direct argument on this topic.