JSFiddle - React, Tailwind, and code Playground

HTML

<form action="" id="form">
  <input type="number" id="square">
  <input type="submit" value="рассчитать">
</form>

JavaScript

var options = [
	{
  	value: 'red',
  	coefficient: 1,
    text: 'красный' >'sds'
   
  },
  {
  	value: 'green',
  	coefficient: 1.2,
    text: 'зеленый'
  },
   {
  	value: 'blue',
  	coefficient: 2.5,
    text: 'синий'
  },
];

function createOption(obj) {
	var option = document.createElement('option');
  var text = document.createTextNode(obj.text);
  option.appendChild(text);
  option.value = obj.value;
  option.dataset.coefficient = obj.coefficient;
  return option;
}

function createSelect(obj) {
	var select = document.createElement('select');
  select.id = 'mySelect';
	obj.forEach(function(option) {
  	select.appendChild(createOption(option));
  });
  document.body.appendChild(select);
}

function calculate(square, coefficient) {
	return square * coefficient;
}

createSelect(options);

document.getElementById('form').addEventListener('submit', function(e){
	e.preventDefault();
  var square = document.getElementById('square').value;
  var select = document.getElementById('mySelect');
  var coefficient = select.options[select.selectedIndex].dataset.coefficient;
  alert('Цена: ' + calculate(square, coefficient));
});