flatten arrays

flatten.js

var arr = [[1,2,[3]],4];

function flatten(arr){
	return arr.reduce(function(pre,curr){
		return pre.concat(curr.constructor === Array ? flatten(curr) : curr);
	}, []);
}
console.log(flatten(arr));

function solutionAvgColor (hex1, hex2) {
  let parseRGB =  (hex) => {
    let bigint = parseInt(hex, 16);
    return [ (bigint >> 16) & 255 , (bigint >> 8) & 255 , bigint & 255 ]
  };

  let [r1, g1, b1] = parseRGB(hex1);
  let [r2, g2, b2] = parseRGB(hex2);


  let rtb = (r1 + r2) / 2;
  let gtb = (g1 + g2) / 2;
  let btb = (b1 + b2) / 2;

  return ( (r, g, b) => ((1 << 24) + (r << 16) + (g << 8) + b).toString(16).slice(1) ) (rtb, gtb, btb);
}

console.log(solutionAvgColor('660000', '000000'));

regex.js

var str = '1.0.1-alpha.2.39';
console.clear();

console.log('first char', str.slice(0,1)); // 1

console.log('last char', str.slice(-1)); // 9


console.log('grab all regular chars except special chars', str.match(/[(?:\d+|\w+)]/g));  // ["1", "0", "1", "a", "l", "p", "h", "a", "2", "3", "9"]

console.log('grab all words except special chars', str.match(/(?:\d+|\w+)/g)); // ["1", "0", "1", "alpha", "2", "39"]

console.log('grab special chars', str.match(/[^(?:\d|\w)]/g)); // [".", ".", "-", ".", "."]