var numArr = Math.floor(Math.random() * 1000).toString().split('');

var number = 4.26; // Your generated double number
output = []; // Array to store each digit
sNumber = number.toString(); // Convert the double to a string so we can split it

for (var i = 0, len = sNumber.length; i < len; i += 1)
{
    output.push(+sNumber.charAt(i));
}

console.log(output);

4, 2, 6