Kata

Implement function sequence, which returns new n-size Array filled according to pattern.

pattern may be:

• a function that takes two: (element, index), one: (element) or any arguments (similar to map function), then filled running this function, in other words: function describes sequence,
• number, string or any other object, then filled by copying, this object n-times.

Examples:

sequence(3, 4); // [4, 4, 4]
sequence(5, []); // [[], [], [], [], []]
sequence(2, "s"); // ["s", "s"]
sequence(5, (x, idx) => idx%2) // [0, 1, 0, 1, 0];
sequence(10, (x, idx) => idx+1) // [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]

Note: Sequences are great to work with functional methods like map, reduce, forEach, every or any. For example:

// sum of numbers 1-10
let sum = sequence(10, (x, idx) => idx+1).reduce((sum, num) => sum + num);

Be careful with long sequences. They are just arrays, every element is created when function is called.

For lazy sequences (elements created when needed) use Iterator.