Using RegExp.test for the callback of Array.some

Question

This works:

var animals = ["caterpillar", "dog", "bird"];
var catMatch = /cat/i;
var catFound = animals.some(function(animalName) {
  return catMatch.test(animalName);
});

console.log(catFound);

But this doesn't

var animals = ["caterpillar", "dog", "bird"];
var catMatch = /cat/i;
var catFound = animals.some(catMatch.test);

console.log(catFound);

Why doesn't the second version work?

Answer 1

RegExp.prototype.test depends on its this value to work. You can pass the required this value to some:

var catFound = animals.some(catMatch.test, catMatch);