Tests a value, x
, against a predicate function. If true
, return fn(x)
. Else, return x
.
Return a function expecting a single value, x
, that returns the appropriate value based on pred
.
代码片段
const when = (pred, whenTrue) => x => (pred(x) ? whenTrue(x) : x);
使用样例
const doubleEvenNumbers = when(x => x % 2 === 0, x => x * 2);
doubleEvenNumbers(2); // 4
doubleEvenNumbers(1); // 1