19 lines
401 B
Markdown
19 lines
401 B
Markdown
### when
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Tests a value, `x`, against a predicate function. If `true`, return `fn(x)`. Else, return `x`.
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`when(pred, whenTrue)` returns a function expecting `x` for better composability.
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```js
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const when = (pred, whenTrue) => (x) => pred(x) ? whenTrue(x) : x;
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```
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```js
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const doubleEvenNumbers = when(
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(x) => x % 2 === 0,
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(x) => x * 2
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);
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doubleEvenNumbers(2) // 4
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doubleEvenNumbers(1) // 1
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```
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