Using pipe() and compose() functions in JavaScript?

Question

I'm reading through a book that is discussing built in JavaScript functions compose() and pipe() for combining functions in functional style programming.

One of the examples seems to suggest running the following as front-end code:

const shuffle =
    (deck, randomizer) => {
        const doShuffle = pipe(
            addRandom(randomizer),
            sortByRandom,
            map(card => card.card)
        );
        return doShuffle(deck);
    };

But when I try running it in the Google Developer console I get back an error saying:

Uncaught ReferenceError: pipe is not defined

I've also tried in Firefox with the same results. What version of JavaScript is needed to make use of these functions?

Am I right to think these functions can only be used with node.js or some kind of pre-compiler like Babel?

Note: I'm running Ubuntu and have tried Chromium and Firefox.

pipe and compose are not native JavaScript functions. It sounds to me like you were reading a functional programming doc from a library like Ramda (ramdajs.com). Just include that library in your page, and your code will work. — Traveling Tech Guy
– Traveling Tech Guy, Commented Oct 15, 2019 at 18:51
@PhilipKirkbride In fact it is, but you clearly haven't conflated the two, so I retract my comment! — msanford
– msanford, Commented Oct 15, 2019 at 23:43

Jay Kariesch · Accepted Answer · 2019-10-15 18:50:36Z

8

pipe and compose aren't native functions. You'll have to add them to your javascript document in order to utilize them. This is an ES6 pipe function that you can use in modern browsers:

const pipe = (...fns) => x => fns.reduce((v, f) => f(v), x)

Here's a compose function:

const compose = (...fns) => x => fns.reduceRight((v, f) => f(v), x);

answered Oct 15, 2019 at 18:50

Jay Kariesch

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1 Comment

Philip Kirkbride Over a year ago

Thank you! It was the case that he did define these somewhere else in the document, but the text was written in a way which made them seem like native functions.

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