JSFiddle - React, Tailwind, and code Playground

JavaScript

var input = [1, 2, 3, 4, 5, 6];
    function isEven(x) { return x % 2 == 0; } // проверяет на четность

    function filter(array, predicate)
    {
        var result = [];
        for (var i = 0; i < array.length; i++)
        {
            if (predicate(array[i]))
            {
                result.push(array[i]);
            }
        }
        return result;
    }


    console.log(filter(input, isEven)); // [2, 4, 6]

    console.log(input); // [1, 2, 3, 4, 5, 6]