Sample Code Inaccurate

[kevinleung23]

first() documentation

Code (in sample):

const fullName = first(
    (t: string) => t === "Bill" && "Bill Barnes", // line 2
    t => t === "Hao" && "Hao Luo",
    t => t === "Kevin" && "Kevin Leung",
);

fullName("Bill").subscribe(console.log);    // Match{ value: "Bill Barnes" }
fullName("Hao").subscribe(console.log);     // Match{ value: "Hao Luo" }
fullName("Yomi").subscribe(console.log);    // undefined

Actual:

Match { score: 1, value: 'Bill Barnes' } // correct
Match { score: 1, value: false } // unexpected
Match { score: 1, value: false } // unexpected

When "Bill" argument is commented out (line 2), results are:

Match { score: 1, value: false }
Match { score: 1, value: 'Hao Luo' }
Match { score: 1, value: false }

If a fall through behavior is correct, samples are wrong.

[howlowck]

In the sample code, any unmatched string will return false (not undefined).

The first function still deems it as a "match" since it's not undefined, and returns the value (which is false).

[billba]

It feels hopelessly naive of you two to expect the sample code to actually work. Wake up and smell the coffee.

[billba]

I'll update the README shortly, but here's the correct code:

const fullName = first(
    (t: string) => t === "Bill" ? "Bill Barnes" : undefined,
    t => t === "Hao" ? "Hao Luo" : undefined,
    t => t === "Kevin" ? "Kevin Leung" : undefined,
);

In the real world I'd probably introduce a helper, e.g.

const getFullName = (
    name: string,
    fullName: string
) => (t: string) => t === name ? fullName : undefined;

const fullName = first(
    getFullName("Bill", "Bill Barnes"),
    getFullName("Hao", "Hao Luo"),
    getFullName("Kevin", "Kevin Leung"),
);

... but that probably would make the samples less clear.