Scans from right, while a test passes.
Alternatives: scanWhile, scanWhileRight, scanUntil, scanUntilRight.
Similar: search, scan, find.
This is part of package extra-array.
array.scanWhileRight(x, ft);
// x: an array
// ft: test function (v, i, x)
// → first index where test passes till endconst array = require("extra-array");
var x = [1, 1, 2, 2, 3, 3, 4, 4];
array.scanWhileRight(x, v => v % 3 !== 0);
// 6 ^
array.scanWhileRight(x, v => v % 2 !== 0);
// 8 ^
array.scanWhileRight(x, v => v % 6 !== 0);
// 0 ^