decimal.js

const nums = [7, 8, 6, 5];

binaryArray = nums.map((element) => {var decimal = Number(element).toString(2); return (decimal.length == 4 ? decimal : "0" + decimal);})
				  .sort((left, right) => {
				  						  var leftDigitCount = (left.match(/1/g) || []).length; 
				  						  var rightDigitCount = (right.match(/1/g) || []).length;

				  						  return (leftDigitCount == rightDigitCount ? parseInt(left, 2) - parseInt(right, 2) : (leftDigitCount > rightDigitCount) ? 1 : -1)

				  						  });