I like this a lot. It's similar to the proposed function bind syntax[1], but a bit more friendly to not-`this`-related use:

    function bindMap(fn) { return this.map(fn) }
    [ 1, 2, 3 ]::bindMap(n => n + 1)
    // standalone use: bindMap.call(arr, fn)

    function pipelineMap(fn) { return arr => arr.map(fn) }
    [ 1, 2, 3 ] |> pipelineMap(n => n + 1)
    // standalone use: pipelineMap(fn)(arr)

(Also nice that it works in a very similar way to decorators, although they won't be interchangeable in most cases, with decorators working on class constructors and property descriptors, instead of just any value.)

Presumably, at most one of these proposals will make it in :)

[1]: https://github.com/zenparsing/es-function-bind