src/main/generic/utils/ArrayUtils.js

/**
 * Returns an iterator over an array in a specific direction.
 * It does *not* handle or reflect changes of the array while iterating it.
 * @memberOf Array
 * @param {boolean} ascending Whether to traverse the array in ascending direction.
 * @returns {{next:function():*, peek:function():*, hasNext:function():boolean}} An iterator.
 */
Array.prototype.iterator = function(ascending=true) {
    let nextIndex = ascending ? 0 : this.length-1;

    return {
        next: () => {
            return nextIndex >= 0 && nextIndex < this.length ?
                this[ascending ? nextIndex++ : nextIndex--] : undefined;
        },
        hasNext: () => {
            return nextIndex >= 0 && nextIndex < this.length;
        },
        peek: () => {
            return nextIndex >= 0 && nextIndex < this.length ?
                this[nextIndex] : undefined;
        }
    };
};