绑定到Array.includes [javascript]

Question

I'm trouble with using this in find if any element in array2 exists in array1:

array2 = [].includes.bind([1,2,3]);
array2(1);   // returns true
array2(9);   // returns false

[5,6,7,8,9].some(array2);        // returns false  GOOD
[3,6,7,8,9].some(array2);        // returns true   GOOD
[6,7,8,9,3].some(array2);        // returns false  OOPS!

[6,7,8,9,3].some(function(i){return array2(i)});  //returns true

Obviously I know one solution to the problem, but I want to know why the [...].some(array2) doesn't work completely.

Answer 1

[6,7,8,9,3].some(array2) doesn't work because Array.prototype.some calls check function with 3 arguments: value, index, entire array while Array.prototype.includes takes 2 arguments . Where the second argument is starting index to search from.

arr.includes(searchElement, fromIndex)

So every next call asks if your first array includes given value starting the given index.