let myArray = [3, 1, 4, 1, 5, 2];
let unwantedElementIndex = 3;

// This line removes 1 element from the array, starting at the unwantedElementIndex
myArray.splice(unwantedElementIndex, 1);

// If you have your custom test to remove an element just go for 
// Higher-Order functions
let myArray = ["someone@example.com", "wrong@email@format.com", "..."];
const emailRegexp = ____;
let allCorrectEmails = myArray.filter(element => emailRegexp.test(element));