Difference Between indexOf and findIndex function of array

Question

I am confused between the difference between the two function indexOf and find Index in an array.

The documentation says

findIndex - Returns

Answer 1

You can also use includes:

[1, 2, 3].includes(2);      // true
[1, 2, 3].includes(4);      // false
[1, 2, 3].includes(3, 3);   // false

but I prefer the indexOf method:

var vals = [ "foo", "bar", 42, "baz" ];
if (~vals.indexOf( 42 )) {
  // found it!
}