8ee50178f3
Correct: `Array.from()` (it’s a static method) Incorrect: `Array.join()` (doesn’t exist; it’s a prototype method) This patch uses the common `#` syntax to denote `.prototype.`.
597 B
597 B
unfold
Builds an array, using an iterator function and an initial seed value.
Use a while loop and Array.prototype.push() to call the function repeatedly until it returns false.
The iterator function accepts one argument (seed) and must always return an array with two elements ([value, nextSeed]) or false to terminate.
const unfold = (fn, seed) => {
let result = [],
val = [null, seed];
while ((val = fn(val[1]))) result.push(val[0]);
return result;
};
var f = n => (n > 50 ? false : [-n, n + 10]);
unfold(f, 10); // [-10, -20, -30, -40, -50]