Array & utility functions

arrayUtilities.js

// Flat 2D array to 1D arry

var arr=[[1,2],[3,4],[5,6]];
var result=[].concat(...arr);
console.log(result);    //output: [ 1, 2, 3, 4, 5, 6 ]
// ------------------------

// Produce a specified number of repeating characters:
function repeat(s,n){
  return [...Array(n+1)].join(s);
}

console.log(repeat("a",5)); //output: aaaaa
console.log(repeat("abc",5)); //output: abcabcabcabcabc
// ------------------------