Javascript: Array.down() and Array.up()

0_info.md

Array.up() and Array.down() let you do semi-basic array processing without nesting Array.map() calls.
This is a silly thing I made in 20 minutes because I thought it would be cursed. You probably shouldn't actually use it.
Somewhat inspired by vectorized functions in python.

1_demo.js

// Function calls between down() and up() will be executed on all elements instead.
["hey","pizza","man"].down().startsWith("m").up()
// => [false, false, true]

// It also works with multiple function calls in a series
"yellow,green,blue".split(",").down().substring(2).repeat(2).up().join("+")
// => "llowllow+eeneen+ueue"

// You can also go multiple levels deep
`5-3,2-4
5-5,1-1`.split("\n").down().split(",").down().split("-").up().up()
// => [
//      [ ["5", "3"], ["2", "4"] ],
//      [ ["5", "5"], ["1", "1"] ]
//    ]

// ^ The last example would usually be written as:
`5-3,2-4
5-5,1-1`.split("\n").map(l => l.split(",").map(e => e.split("-")))

2_implementation.js

const UP = Symbol("up");
Array.prototype.down = function () {
    console.assert(Array.isArray(this));
    return wrap(this);
}

Array.prototype.up = function () {
    console.assert(Array.isArray(this));

    let upper = this[UP];
    if (!upper) throw new Error("this is not a wrapped array");
    return upper
}

function wrap(target) {
    let fake = new Proxy(target, {
        get: function (target, prop) {
            if (prop == UP) return target;
            let res = makeDeepFunc(target, prop);
            return res
        }
    })
    
    return fake
}

function makeDeepFunc(target, name) {
    // If the elements don't have UP, then an up() call is actually meant for the array and not for the elements
    if (name == "up" && !target[0][UP]) return target.up;

    return (...args) => {
        let result = [];
        for (let item of target) {
            result.push(item[name](...args));
        }
        return wrap(result)
    }
}